Abstract:
A circuit for synchronizing an internal time signal to an external time signal includes a first timer, a second timer, and a comparator. The first timer repetitively increments and outputs a first time signal. The second timer repetitively outputs a second time signal. The comparator drives an active comparator signal if the first time signal is greater than the second time signal, or otherwise an inactive signal. The first timer saves the second time signal as the first time signal in response to a control signal derived from the inactive comparator signal and repetitively increments and outputs the first time signal. Alternatively, the first timer freezes, i.e., preventing the repetitive incrementing, of the first time signal in response to a control signal derived from the active comparator signal. The second timer repetitively increments and outputs the second time signal in response to a control signal derived from the active comparator signal. When the first time signal becomes less than or equal to the second time signal, the first timer unfreezes the first time signal in response to a control signal derived from the inactive comparator signal.

Description:
CROSS-REFERENCE TO SOURCE CODE APPENDIX 
     Appendix A, which is part of the present disclosure, contains VERILOG source code for implementing one embodiment of this invention as described more completely below. 
     A portion of the present disclosure contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever. 
     BACKGROUND 
     IEEE Standard for a High Performance Serial Bus (“IEEE 1394”) provides that each isochronous-capable node must implement, among others, a CYCLE_TIME register storing a 32 bit time signal (“CYCLE_TIME”) updated by a free-running 24.576 MHz clock. An isochronous-capable node is a device that can transfer isochronous data over a serial bus to other isochronous-capable nodes. In isochronous data transfer, data is broadcasted on assigned channels with guaranteed bandwidth allocation. 
     Signal CYCLE_TIME in the CYCLE_TIME register comprises a seven bit second_count field, a thirteen bit cycle_count field, and a twelve bit cycle_offset field. The cycle_offset field increments on each tick of the 24.576 MHz clock with the exception that an increment from the value of 3071 causes a wraparound to zero and a carry into the cycle_count field. The cycle_count field increments on each carry from the cycle_offset field with the exception that an increment from the value of 7999 causes a wraparound to zero and a carry into the cycle_count field. The second_count field increments on each carry from the cycle_count field with the exception that an increment from the value of 127 causes a wraparound to zero. 
     The CYCLE_TIME register must further be synchronized to a time signal (“MASTER_TIME”) contained in a cycle start packet (“CSP”) transmitted by a node known as the master node. Specifically, IEEE 1394 standard provides that “a cycle slave must implement a synchronization mechanism between the cycle start packets and the CYCLE_TIME register such that time, as observed by the values of the CYCLE_TIME register, never appears to move backwards.” IEEE Standard for a High Performance Serial Bus, p.212, The Institute of Electrical And Electronics Engineers, Inc., 1996. However, the details of the synchronization mechanism are left to the individual device manufacturers. 
     The IEEE 1394 standard is available from the Institute of Electrical and Electronic Engineers located at 345 East 47th Street, New York, N.Y. 100107-2394. The IEEE 1394 can be purchased directly from the IEEE. The IEEE 1394 standard is hereby incorporated by reference in its entirety. 
     An implementation of IEEE 1394 standard includes a first node  600  and a second node  700  coupled through a cable  614  (FIG.  1 A). Node  600  includes an application logic  602 , a link controller  604 , and a PHY chip  606 . Circuitry included in application logic  602  (FIG. 1B) depends on the application. For example, for a set top box, logic  602  includes RF tuner, IF tuner, forward error correction circuit, MPEG2 transport stream decoder, MPEG2 video decoder, MPEG2 audio decoder, smartcard interface, and memory (ROM and RAM). Similarly, node  700  includes another application logic  702 , a link controller  704 , and a PHY chip  706 . Link controller  604  (FIG. 1B) includes a packet transmitter  608 , a packet receiver  610 , and a cycle control  612 . Cycle control  612  includes a register  603  conforming to the IEEE 1394 standard. PHY chip  606  also includes, for example, 24.576 MHz clock  616 . Note that when node  600  is in master mode, packet transmitter  608  uses the value of register  603  to generate a cycle start packet, as described in the IEEE 1394 standard. 
     SUMMARY 
     In accordance with the present invention, a circuit for synchronizing a first time signal to a second time signal includes a first timer, a second timer, and a comparator. The first timer repetitively increments (once during each clock cycle) the first time signal and drives the first time signal on an output bus of the first timer. The second timer saves a time signal from a master node as a second time signal and drives the second time signal on an output bus of the second timer. The comparator is coupled to the output bus of the first timer and the output bus of the second timer. The comparator compares the first time signal and the second time signal. When the second time signal is less than the first time signal, the first timer stops incrementing the first time signal, i.e., freezes the first time signal. At the same time, the second timer starts to repetitively increment (once during each clock cycle) the second time signal. As before, the second timer continues to drive the second time signal on the output bus of the second timer. When the second time signal is equal to the first time signal, the first timer starts again to repetitively increment and drive the first time signal on the output bus of the first timer. At the same time, the second timer stops incrementing the second time signal. 
     In one embodiment of the present invention, the first timer includes a first register coupled to a first multiplexer, together hereafter referred to as a “first selective register.” The first timer also includes an incrementor coupled to a second multiplexer, together hereafter referred to as a “selective incrementor.” To increment the first time signal, the output bus of the first register is coupled to input port of the incrementor through the second multiplexer and the output bus of the incrementor is coupled to the input port of the first register. To freeze the first time signal, the output bus of the first register is coupled to the input port of the first register through the first multiplexer. 
     In another embodiment, the second timer includes a second register coupled to a third multiplexer, together hereafter referred to as a “second selective register,” and also includes the selective incrementor (described above). To increment the second time signal, the output bus of the second register is coupled to input port of the incrementor through the second multiplexer and the output bus of the incrementor is coupled to the input port of the second register through the third multiplexer. In one embodiment, the first timer and the second timer use separate incrementors to increment the first time signal and the second time signal, respectively. In another embodiment, the first timer and the second timer use a single incrementor to increment the first time signal and the second time signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A illustrates, in a high level block diagram, prior art architecture of IEEE 1394. 
     FIG. 1B illustrates, in a high level block diagram, a prior art link controller. 
     FIG. 2A illustrates, in a high level block diagram, a circuit used to synchronize an internal time signal (“CYCLE_TIME”) to an external time signal (“MASTER_TIME”) in accordance with one embodiment of the present invention. 
     FIG. 2B illustrates, in a flow chart, a method used to synchronize an internal time signal to an external time signal in accordance to one embodiment of the present invention. 
     FIG. 2C illustrates, in a state diagram, a state machine used to implement the circuit illustrated in FIG. 2A in accordance with the method illustrated in FIG.  2 B. 
     FIG. 3A illustrates, in an intermediate-level block diagram, an implementation of the circuit illustrated in FIG.  2 A. 
     FIG. 3B illustrates, in a state diagram, a state machine used to implement the circuit illustrated in FIG. 3A in accordance with the method illustrated in FIG.  2 B. 
     FIG. 4A illustrates, in an intermediate-level block diagram, another implementation of the circuit illustrated in FIG.  2 A. 
     FIG. 4B illustrates, in a state diagram, a state machine used to implement the circuit illustrated in FIG. 4A in accordance with the method illustrated in FIG.  2 B. 
     FIG. 5A illustrates, in a low level block diagram, the circuit illustrated in FIG.  4 A. 
     FIG. 5B illustrates, in a state diagram, a state machine used to implement the circuit illustrated in FIG. 5A in accordance with the method illustrated in FIG.  2 B. 
    
    
     DETAILED DESCRIPTION 
     A cycle control  512  (FIG. 2A) in accordance with the present invention synchronizes a first time signal to a second time signal by use of a first timer  100  (“cycle timer  100 ”), a second timer  200  (“shadow timer  200 ”) and a comparator  300 . Specifically, first timer  100  repetitively increments (once during each clock cycle) an internal time signal (also called “first time signal”, and “CYCLE_TIME”), and drives the internal time signal on an output bus  110  (FIG.  2 A). Shadow timer  200  saves an external time signal (also referred to “MASTER_TIME”) and increments the saved time signal and supplies the incremented value on an output bus  210  as a second time signal. 
     Comparator  300  is coupled to output bus  110  and output bus  210  of the timers  100  and  200  respectively. Comparator  300  compares the two time signals from the timers  100  and  200 , and drives a resulting signal on line  306  to state machine  400 . When the second time signal is less than the first time signal, state machine  400  stops incrementing the first time signal, i.e. freezes the first time signal. At the same time, state machine  400  causes shadow timer  200  to repetitively increment the second time signal. When the second time signal is equal to the first time signal, state machine  400  causes cycle timer  100  to again repetitively increment the first time signal. At the same time, state machine  400  causes shadow timer  200  to stop incrementing the second time signal. Therefore, state machine  400  alternates between incrementing the two timer signals, depending on their values relative to one another. 
     The first time signal is used by various circuits, such as one or more of: A packet transmitter (when acting in master mode as described above), a packet parser (which parses a packet received by the packet receiver using a format similar or identical to the packet format defined in section 6.2 of the IEEE 1394 specification), and a packet generator (which generates a packet supplied to the packet transmitter). 
     In one implementation, application logic  522  (FIG. 2A) includes a packet parser  523  that parses a data field, e.g., in a IEEE 1394 packet by use of a format defined in FIG. 6 of the IEC 61883-1 specifications (first edition, published 1998 and incorporated by reference herein in its entirety), to recover a time stamp, and holds the packet until the time stamp matches the first time signal. See FIG. 4 of IEC 61883-4 for a description of the exemplary method (first edition, published 1998, and incorporated by reference herein in its entirety). In this implementation, packet generator  524  inserts the first time signal into a packet as the time stamp in a similar manner. Also in this implementation, application logic  522  includes an I/O circuit (not labeled) that is used to transfer a first time signal to another device in logic  522 , e.g., a packet flow controller. 
     In one embodiment, cycle timer  100  includes a first port  102 A (also called “first time port”) and, a second port (also called “second time port”)  104 A, and receives thereon time signals from application logic  522  and from a PHY device  525  respectively. In addition, cycle timer  100  includes a command port  106 A, a clock terminal  108 A, and an output bus  110 . Port  102 A is coupled to a time bus  508 , which carries a time signal (“NEW_TIME”) (e.g., 32 bits wide) from an external source, for example, application logic  522  which is included in node  500  (FIG.  2 A). Port  104 A is coupled to a bus  502  (“MASTER_TIME bus”) from a packet receiver  610  (FIG.  1 B), which carries a time signal (“MASTER_TIME”) (e.g., 32 bits wide) from the cycle start packet transmitted by the master node. Port  106 A is coupled to a command bus  402  (e.g., 2 bits wide), which carries command signals from state machine  400 . Terminal  108 A is coupled to a clock line  506 , which carries a CLOCK signal from PHY device  525 . PHY device  525  conforms to e.g. Annex J of the IEEE 1394 standard (e.g. see page 333 of the edition published on 1995 which is incorporated by reference above). 
     As noted above, cycle timer  100  stores, drives (i.e., outputs), and increments a signal CYCLE_TIME that is provided by cycle control circuit  512  to the other components of a link controller. Cycle timer  100  operates in four modes. In a first mode (“first cycle timer mode”), cycle timer  100  drives signal CYCLE_TIME on bus  110  at, for example, each rising edge in clock signal from oscillator received on terminal  108 A and then increments signal CYCLE_TIME. In a second mode (“second cycle timer mode”), cycle timer  100  saves a time signal (“NEW_TIME”) received on port  102 A as signal CYCLE_TIME, where signal NEW_TIME has the same structure as signal CYCLE_TIME. In a third mode (“third cycle timer mode”), cycle timer  100  saves signal MASTER_TIME received on port  104 A as signal CYCLE_TIME, where signal MASTER_TIME has the same structure as signal CYCLE_TIME. In a fourth mode (“fourth cycle timer mode”), cycle timer  100  drives signal CYCLE_TIME on bus  110  at, for example, each rising edge in the signal received on clock terminal  108 A without incrementing signal CYCLE_TIME, thereby freezing signal CYCLE_TIME. The above operation modes of cycle timer  100  are controlled through command signals received on port  106 A from state machine  400 . 
     Shadow timer  200  includes a first port (also called “first time port”)  204 A on which the external time signal is received, a terminal (also called “command terminal”)  206 A on which signals from state machine  400  are received. Shadow timer  200  also has a clock terminal  208 A, and a time bus  210 . Port  204 A is coupled to MASTER_TIME bus  502  and terminal  208 A is coupled to clock line  506 . Terminal  206 A is coupled to a command line  410 , which carries command signals from state machine  400 . 
     Shadow timer  200  stores, drives, and increments a SHADOW_TIME signal that has the same structure as signal CYCLE_TIME. Shadow timer  200  operates in two modes. In a first mode (“first shadow timer mode”), shadow timer  200  saves signal MASTER_TIME received on port  204 A as the SHADOW_TIME signal and drives the SHADOW_TIME signal on bus  210  at, for example, each rising edge in the signal received on clock terminal  208 A. In a second mode (“second shadow timer mode”), shadow timer  200  drives the SHADOW_TIME signal on bus  210  at, for example, each rising edge in the signal received on bus  110  and then increments the SHADOW_TIME signal. The above described modes of shadow timer  200  are controlled through command signals received on terminal  206 A, e.g. from state machine  400 . 
     Comparator  300  includes a first time port  302 , a second time port  304 , and a comparator result line  306 . Port  302  is coupled to time bus  110  from cycle timer  100  and port  304  is coupled to time bus  210  from shadow timer  200 . 
     Comparator  300  compares the value of signal SHADOW_TIME received from bus  210  to the value of signal CYCLE_TIME received from bus  110 . Comparator  300  drives, for example, an active signal on line  306  if the value of signal CYCLE_TIME is greater than the value of signal SHADOW_TIME. If the value of signal CYCLE_TIME is less than or equal to the value of signal SHADOW_TIME, comparator  300  outputs an inactive signal on line  306 . 
     State machine  400  includes a terminal (also called “cycle start packet” (“CSP”) terminal)  404  to receive an active signal from packet receiver  610  if a new CSP is available, or otherwise an inactive signal. An active signal on CSP line  504  connected to terminal  404  means that cycle control  512  must synchronize signal CYCLE_TIME to signal MASTER_TIME contained in the CSP to comply with the requirements of IEEE 1394. State machine  400  also includes a clock terminal  406 , a comparator result terminal  408 , a command bus  402 , and command line  410 . Clock terminal  406  is coupled to the clock line  506 . Comparator result terminal  408  is coupled to comparator result line  306  that is coupled to comparator  300 . State machine  400  also has a terminal  407  (also called “load NEW_TIME terminal”) which is coupled to a line (also called “load NEW_TIME line”)  507 , which carries, e.g., an active signal if an external source, e.g., a user who supplies the signal via computer software, wants to save a signal NEW_TIME from bus  508  into cycle timer  100 . 
     State machine  400  starts with action  12  (FIG.  2 B). Action  12  is followed by action  14 . In action  14 , state machine  400  commands cycle timer  100  to drive signal CYCLE_TIME on bus  110  at each rising edge in the signal (“rising clock edge”) received on terminal  108 A and then increment signal CYCLE_TIME. State machine  400  also commands shadow timer  200  to save signal MASTER_TIME received on port  204 A as the SHADOW_TIME signal and drive the SHADOW_TIME signal on bus  210  at each rising clock edge received on clock terminal  208 A. To do this, state machine  400  drives a signal on command bus  402  for cycle timer  100  to enter into the previously described first cycle timer mode, and a command on command line  410  for shadow timer  200  to enter the first shadow timer mode. 
     In one embodiment, action  14  occurs simultaneously with decisional action  16 , decisional action  20 , and decisional action  21 . In action  16 , state machine  400  determines if it must save a signal NEW_TIME into cycle timer  100 . State machine  400  must save a signal NEW_TIME into cycle timer  100  when it receives an active signal on load signal NEW_TIME terminal  407 . An active signal on terminal  407  indicates that an external source, e.g., a computer software, wants to save a signal NEW_TIME into cycle timer  100 . If state machine  400  must save a signal NEW_TIME into cycle timer  100 , action  16  is followed by action  18 . Otherwise, action  16  is followed by action  20 . 
     In action  18 , state machine  400  commands cycle timer  100  to save signal NEW_TIME received on port  102 A as signal CYCLE_TIME of state machine  400 . To do this, state machine  400  drives a signal on command bus  402  for cycle timer  100  to enter into the previously described second cycle timer mode. Action  18  is followed by action  14 . 
     In action  20 , state machine  400  determines if signal MASTER_TIME is valid, i.e., a new signal MASTER_TIME. Signal MASTER_TIME is valid if state machine  400  receives an active signal on CIP availability line  504 . If signal MASTER_TIME is valid, action  20  is followed by action  21 . Otherwise, action  20  is followed by action  14 . 
     In action  21 , state machine  400  determines if signal SHADOW_TIME is greater than or equal to signal CYCLE_TIME, indicated by an inactive signal on terminal  408 . Please note that the SHADOW_TIME signal has the same value as signal MASTER_TIME contained in the CSP because shadow timer  200  is still in the first shadow timer mode. If so, action  21  is followed by action  22 . Otherwise, action  20  is followed by action  26 . 
     In action  22 , state machine  400  commands cycle timer  100  to save signal MASTER_TIME received on port  104 A as signal CYCLE_TIME. To do this, state machine  400  drives a signal on bus  402  for cycle timer  100  to enter the previously described third cycle timer mode. Action  22  is followed by action  14 . 
     In action  26 , state machine  400  commands cycle timer  100  to drive signal CYCLE_TIME on bus  110  at each rising clock edge received on terminal  108 A without incrementing, i.e., freezing, signal CYCLE_TIME. State machine  400  also commands shadow timer  200  to drive the SHADOW_TIME signal on bus  210  at each rising clock edge received on terminal  208 A and then increment the SHADOW_TIME signal. To do this, state machine  400  drives a signal on command bus  402  for cycle timer  100  to enter the fourth cycle timer mode, and a command on line  410  for shadow timer  200  to enter the second shadow timer mode. Action  26  is followed by action  28 . 
     In action  28 , state machine  400  determines if it must unfreeze signal CYCLE_TIME in cycle timer  100 . State machine  400  must unfreeze signal CYCLE_TIME in cycle timer  100  if signal SHADOW_TIME is greater than or equal to signal CYCLE_TIME, indicated by an inactive signal on terminal  408 . If state machine  400  must unfreeze signal CYCLE_TIME, action  28  is followed by action  14 . Otherwise, action  28  is followed by action  26 . 
     State machine  400  (FIG. 2C) starts in state  0  (“zero state”). State machine  400  transitions from state  0  to state  1  on receiving a rising clock edge on clock terminal  406 . 
     To transition from state  0  to state  1  (“normal state”), state machine  400  drives (1) a command on command bus  402  for cycle timer  100  to enter into the first cycle timer mode and (2) a command on command line  410  for shadow timer  200  to enter the first shadow timer mode. The conditions and actions for the transition from state  0  to state  1  are captioned in box  31  of FIG.  2 C. 
     State machine  400  transitions from state  1  to state  2  (“load state”) on the condition of state machine  400  receiving an active signal on terminal  407 . As previously described, terminal  407  is coupled to load NEW_TIME line  507 , which carries an active signal if an external source, e.g., a computer software, wants to save a signal NEW_TIME on bus  508  into cycle timer  100 . 
     To transition from state  1  to state  2 , state machine  400  drives a signal on command bus  402  for cycle timer  100  to enter into the second cycle timer mode. The shadow timer mode is irrelevant in the transition from state  1  to state  2 . The conditions and actions for the transition from state  1  to state  2  are captioned in box  51  of FIG.  2 C. 
     State machine  400  transitions from state  2  to state  1  on the condition of state machine  400  receiving a rising clock edge on terminal  406 . To transition from state  2  to state  1 , state machine  400  drives (1) a signal on command bus  402  for cycle timer  100  to enter into the first cycle timer mode and (2) a signal on command line  410  for shadow timer  200  to enter the first shadow timer mode. The conditions and actions for the transition from state  2  to state  1  are captioned in box  52  of FIG.  2 C. 
     State machine  400  transitions from state  1  to state  3  (“update state”) on the conditions of state machine  400  receiving of an active signal on terminal  404  and an inactive signal on terminal  408 . As previously described, terminal  404  is coupled to a CSP availability line  504 , which carries an active signal if a new CSP is available. Terminal  408  is coupled to coupled to comparator result line  306 , which carries an inactive signal if the CYCLE_TIME is less than or equal to the SHADOW_TIME signal. 
     To transition from state  1  to state  3 , state machine  400  drives a signal on command bus  402  for the cycle timer to enter the third cycle timer mode. The shadow timer mode is irrelevant in the transition from state  1  to state  3 . The conditions and actions for the transition from state  1  to state  3  are as follows: 
     State machine  400  transitions from state  3  to state  1  on the condition of state machine  400  receiving a rising clock edge on clock terminal  406 . To transition from state  3  to state  1 , state machine  400  drives (1) a signal on command bus  402  for cycle timer  100  to enter the first cycle timer mode and (2) a signal command line  410  for shadow timer  200  to enter the first shadow timer mode. The conditions and actions for the transition from state  3  to state  1  are captioned in box  62  of FIG.  2 C. 
     State machine  400  transitions from state  1  to state  4  on the conditions of state machine  400  receiving an active signal on terminal  404  and an active signal on terminal  408 . To transition from state  1  to state  4 , state machine  400  drives (1) a signal on command bus  402  for cycle timer  100  to enter the fourth cycle timer mode and (2) a signal on command line  410  to shadow timer  200  to enter the second shadow timer mode. The conditions and actions for the transition from state  1  to state  4  are captioned in box  71  of FIG.  2 C. 
     State machine  400  transitions from state  4  to state  1  on the condition of state machine receiving an inactive signal on terminal  408 . To transition from state  4  to state  1 , state machine  400  drives (1) a signal on command bus  402  for cycle timer  100  to enter the first cycle timer mode and (2) a signal on command line  410  for shadow timer  200  to enter the first shadow timer mode. The conditions and actions for the transition from state  4  to state  1  are captioned in box  72  of FIG.  2 C. 
     In one embodiment, cycle timer  100  (FIG. 3A) includes a cycle register (as called “selective cycle register”)  10  and a first incrementor  20 , and shadow timer  200  includes another selective register (also called “selective shadow register”)  30  and a second incrementor  40 . 
     A selective register as used herein is a circuit that can select an input source from a plurality of input sources, store the signal carried by the selected input source and supply the stored signal after one clock delay. In this embodiment, selective cycle register  10  includes a first time input port  102 B, a second time input port  104 B, a command port  106 B, a clock terminal  108 B, time bus  110 , a third time input port  116 A, and a fourth time input selective port  114 A, where port  114 A is coupled to time bus  110 . Thus, selective cycle register  10  can store therein a time signal from any of the following four ports: Port  102 B, port  104 B, port  1114 A, and port  116 A. Selective cycle register  10  outputs the time signal on time bus  110  with one clock delay. Port  102 B, port  104 B, port  106 B, and terminal  108 B are respectively coupled to port  102 A, port  104 A, port  106 A, and terminal  108 A. Port  102 B, port  104 B, port  106 B, and terminal  108 B respectively receive the time signal on bus  508  (NEW_TIME), the time signal on bus  502  (MASTER_TIME), command signals on bus  402 , and the clock signal on line  506 . 
     Each of incrementors  20  and  40  increments the value of an input signal (e.g. 32 bit signal) by one. In one implementation, incrementor  20  increments the value field of signal CYCLE_TIME. Incrementor  20  includes an incrementor port  118  and an incrementor bus  120 . Incrementor port  118  is coupled to time bus  110 , and incrementor bus  120  (carrying the incremented CYCLE_TIME) is coupled to port  116 A of selective cycle register  10 . 
     Selective shadow register  30  includes a first time port  204 B, a command terminal  206 B, a clock terminal  208 B, time output bus  210 , and a selective port  216 A. Thus, selective shadow register  30  can select a time signal from one of port  204 B and port  216 A, and output the time signal on bus  210 B with one clock delay. Port  204 B, terminal  206 B, and terminal  208 B are respectively coupled to port  204 A, terminal  206 A, and terminal  208 A. Port  204 B, terminal  206 B and terminal  208 B respectively receive the time signal on bus  502  (MASTER_TIME), command signals on line  410 , and the clock signal on line  506 . 
     In one implementation, incrementor  40  increments the value of the signal SHADOW_TIME. Incrementor  40  includes an incrementor port  218  and an incrementor bus  220 . Incrementor port  218  is coupled to time bus  210  of selective shadow register  30 , and incrementor bus  220  (carrying the incremented SHADOW_TIME) is coupled to selective port  216 A. 
     The previously discussed cycle timer modes are now explained in relation to one implementation having selective cycle register  10  and incrementor  20 . In the first cycle timer mode, cycle timer  100  drives signal CYCLE_TIME on bus  110  at each rising clock edge received on terminal  108 A and then increment signal CYCLE_TIME. To do so, selective cycle register  10  selects port  116 A of incrementor  20  as its input source. Thus, at each rising clock edge, selective cycle register  10  drives onto time bus  110  a time signal it received at the previous rising clock edge at port  116 A from incrementor  20 , and incrementor  20  constantly increments the time signal it receives at port  118  from selective cycle register  10  and drives the incremented time signal on bus  120 . 
     In the second cycle timer mode, cycle timer  100  saves a signal CYCLE_TIME received on port  102 A as signal CYCLE_TIME of state machine  400 . To do this, selective cycle register  10  selects port  102 B as its input source. 
     In the third cycle timer mode, cycle timer  100  saves signal MASTER_TIME received on port  104 A as signal CYCLE_TIME of state machine  400 . To do so, selective cycle register  10  selects port  104 B as its input source for one clock cycle. 
     In the fourth cycle timer mode, cycle timer  100  drives signal CYCLE_TIME on bus  110  at each rising clock edge received on bus  108 A without incrementing signal CYCLE_TIME, thereby freezing signal CYCLE_TIME. To do this, selective cycle register  10  selects port  114 A as its input source. Thus, selective cycle register falls into a loop where it drives the same time signal it generated at the previous rising clock edge. The above operation modes of cycle timer  100  are controlled by command signals from state machine  400  received on port  106 B of selective cycle register  10  in accordance to the state diagram illustrated in FIG.  2 C. 
     The previously discussed shadow timer modes are now explained in relation to the implementation having selective shadow register  30  and incrementor  40 . In the first shadow timer mode, shadow timer  200  saves signal MASTER_TIME received on port  204 A as the SHADOW_TIME signal and drives SHADOW_TIME on bus  210  at each rising clock edge received on bus  110 . To do this, selective shadow register  30  selects port  204 B as its input source. 
     In the second shadow timer mode, shadow timer  200  drives the SHADOW_TIME signal on time bus  210  at each rising clock edge received terminal  208 A and then increments the SHADOW_TIME signal. To do this, selective shadow register  30  selects port  216 A as its input source. Thus, at each rising clock edge, selective shadow register  30  drives onto time bus  210  a time signal it received at the previous rising clock edge at port  216 A from incrementor  40 , and incrementor  40  constantly increments the time signal it receives at port  218  from selective shadow register  30  and drives the incremented time signal on bus  220 . The above operation modes of shadow timer  200  are controlled through command signals received from state machine  400  on terminal  206 B of selective shadow register  30  in accordance to the state diagram illustrated in FIG.  2 C. 
     FIG. 3B illustrates a state diagram for the embodiment illustrated in FIG. 3A in accordance with the method illustrated in FIG.  2 B. State machine  400  starts in state  0  (“zero state”). State machine  400  transitions from state  0  to state  1  on the condition of state machine  400  receiving a rising clock edge on clock terminal  406 . To transition from state  0  to state  1  (“normal state”), state machine  400  drives (1) a command on command bus  402  for selective cycle register  10  to select port  116 A as its input source and (2) a command on command line  410  for selective shadow register  30  to select port  204 A as its input source. The conditions and actions for the transition from state  0  to state  1  are captioned in box  34  of FIG.  3 B. 
     State machine  400  transitions from state  1  to state  2  (“load state”) on the condition of state machine  400  receiving an active signal on terminal  407 . To transition from state  1  to state  2 , state machine  400  drives a signal on command bus  402  for selective cycle register  10  to select port  102 B as its input source. The action of selective shadow register  30  is irrelevant for the transition from state  1  to state  2 . The conditions and actions for the transition from state  1  to state  2  are captioned in box  57  of FIG.  3 B. 
     State machine  400  transitions from state  2  to state  1  on the condition of state machine  400  receiving a rising clock edge on terminal  406 . To transition from state  2  to state  1 , state machine  400  drives (1) a signal on command bus  402  for selective cycle register  10  to select port  116 A as its input source and (2) a signal on command line  410  for selective shadow register  30  to select port  204 A as its input source. The conditions and actions for the transition from state  2  to state  1  are captioned in box  58  of FIG.  3 B. 
     State machine  400  transitions from state  1  to state  3  (“update state”) on the conditions of state machine  400  receiving of an active signal on terminal  404  and an inactive signal on terminal  408 . To transition from state  1  to state  3 , state machine  400  drives a signal on command bus  402  for selective cycle register  10  to select port  104 B as its input source. The action of selective shadow register  30  is irrelevant for the transition from state  1  to state  3 . The conditions and actions for the transition from state  1  to state  3  are captioned in box  68  of FIG.  4 B. 
     State machine  400  transitions from state  3  to state  1  on the condition of state machine  400  receiving a rising clock edge on clock terminal  406 . To transition from state  3  to state  1 , state machine  400  drives (1) a signal on command bus  402  for selective cycle register  10  to select port  116 A as its input source and (2) a signal on command line  410  for selective shadow register  30  to select port  204 A as its input source. The conditions and actions for the transition from state  3  to state  1  are captioned in box  69  of FIG.  3 B. 
     State machine  400  transitions from state  1  to state  4  on the conditions of state machine  400  receiving an active signal on terminal  404  and an active signal on terminal  408 . To transition from state  1  to state  4 , state machine  400  drives (1) a signal on command bus  402  for selective cycle register  10  to select port  114 A as its input source and (2) a signal on command line  410  for selective shadow register  30  to select port  216 A as its input source. The conditions and actions for the transition from state  1  to state  4  are captioned in box  77  of FIG.  3 B. 
     State machine  400  transitions from state  4  to state  1  on the condition of state machine receiving an inactive signal on terminal  408 . To transition from state  4  to state  1 , state machine  400  drives (1) a signal on command bus  402  for selective cycle register  10  to select port  116 A as its input source and (2) a signal on command line  410  for selective shadow register  30  to select port  204 A as its input source. The conditions and actions for the transition from state  4  to state  1  are captioned in box  78  of FIG.  3 B. 
     FIG. 4A illustrates another embodiment state machine  400  illustrated in FIG. 3A, where cycle timer  100  includes selective cycle register  10  and a selective incrementor  50 , and shadow timer  200  includes selective shadow register  30  and selective incrementor  50 . Selective incrementor  50  is an incrementor that can select an input source from a plurality of input sources and increment a signal from that that input source. Selective incrementor  50  includes a selective incrementor port  122 A coupled to time bus  110 , a selective incrementor port  124 A coupled to time bus  210 , a selective incrementor bus  126 A coupled to port  116 A of selective cycle register  10  and port  216 A of selective shadow register  30 , and a command terminal  128 A. Thus, selective incrementor  50  can select an input source from port  122 A (output from selective cycle register  10 ) and  124 A (output from selective shadow register  30 ), and output the signal on bus  126 A. In one implementation, selective incrementor  50  increments the value of signal CYCLE_TIME or the SHADOW_TIME signal. 
     In this embodiment, cycle timer  100  and shadow timer  200  are able to share selective incrementor  50 , which replaces incrementor  20  and incrementor  40 , because incrementor  20  and incrementor  40  are never used concurrently. In this embodiment, state machine  400  further includes a command line  412  coupled to terminal  128 A to control the selection of the input source for selective incrementor  50 . 
     The previously discussed cycle timer modes are now explained in relation to selective cycle register  10  and selective incrementor  50  of FIG.  4 A. In the first cycle timer mode, cycle timer  100  drives signal CYCLE_TIME on bus  110  at each rising clock edge received on terminal  108 A and then increment signal CYCLE_TIME. To do so, selective cycle register  10  selects port  116 A as its input source and selective incrementor  50  selects port  122 A as its input source. Thus, at each rising clock edge, selective cycle register  10  drives onto time bus  110  a time signal it received at the previous rising clock edge at port  116 A from selective incrementor  50 , and selective incrementor  50  constantly increments the time signal it receives at port  122 A from selective cycle register  10  and drives the incremented time signal on bus  126 . 
     The second, third, and fourth cycle timer mode remain unchanged. The above operation modes of cycle timer  100  are controlled by command signals from state machine  400  received on port  106 B of selective cycle register  10  and port  128 A of selective incrementor  50  in accordance to the state diagram illustrated in the to be described FIG.  4 B. 
     The previously discussed shadow timer modes are now explained in relation to selective shadow register  30  and selective incrementor  50  of FIG.  4 A. The first shadow mode remains unchanged. 
     In the second shadow timer mode, shadow timer  200  drives the SHADOW_TIME signal on time bus  210  at each rising clock edge received terminal  208 A and then increments the SHADOW_TIME signal. To do this, selective shadow register  30  selects port  216 A as its input source and selective incrementor  50  selects port  124 A as its input source. Thus, at each rising clock edge, selective shadow register  30  drives onto time bus  210  a time signal it received at the previous rising clock edge at port  216 A from selective incrementor  50 , and selective incrementor  50  constantly increments the time signal it receives at port  124 A from selective shadow register  30  and drives the incremented time signal on bus  126 . The above operation modes of shadow timer  200  are controlled through command signals received from state machine  400  on command terminal  206 B of selective shadow register  30  and command terminal  128 A of selective incrementor  50  in accordance to the state diagram illustrated in the to be described FIG.  4 B. 
     FIG. 4B illustrates a state diagram for the embodiment illustrated in FIG.  4 A. State machine  400  starts in state  0  (“zero state”). State machine  400  transitions from state  0  to state  1  on the condition of state machine  400  receiving a rising clock edge on clock terminal  406 . To transition from state  0  to state  1  (“normal state”), state machine  400  drives (1) a signal on command bus  402  for selective cycle register  10  to select port  116 A as its input source, (2) a signal on command line  410  for selective shadow register  30  to select port  204 A as its input source, and (3) a signal on command line  412  for selective incrementor  50  to select port  122 A as its input source. The conditions and actions for the transition from state  0  to state  1  are captioned in box  32  of FIG.  4 B. 
     State machine  400  transitions from state  1  to state  2  (“load state”) on the condition of state machine  400  receiving an active signal on terminal  407 . To transition from state  1  to state  2 , state machine  400  drives a signal on command bus  402  for selective cycle register  10  to select port  102 B as its input source. The actions of selective shadow register  30  and selective incrementor  50  are irrelevant for the transition from state  1  to state  2 . The conditions and actions for the transition from state  1  to state  2  are captioned in box  53  of FIG.  4 B. 
     State machine  400  transitions from state  2  to state  1  on the condition of state machine  400  receiving a rising clock edge on terminal  406 . To transition from state  2  to state  1 , state machine  400  drives (1) a signal on command bus  402  for selective cycle register  10  to select port  116 A as its input source, (2) a signal on command line  410  for selective shadow register  30  to select port  204 A as its input source, and (3) a signal on command line  412  for selective incrementor  50  to select port  122 A as its input source. The conditions and actions for the transition from state  2  to state  1  are captioned in box  54  of FIG.  4 B. 
     State machine  400  transitions from state  1  to state  3  (“update state”) on the conditions of state machine  400  receiving of an active signal on terminal  404  and an inactive signal on terminal  408 . To transition from state  1  to state  3 , state machine  400  drives a signal on command bus  402  for selective cycle register  10  to select port  104 B as its input source. The actions of selective shadow register  30  and selective incrementor  50  are irrelevant for the transition from state  1  to state  3 . The conditions and actions for the transition from state  1  to state  3  are captioned in box  63  of FIG.  4 B. 
     State machine  400  transitions from state  3  to state  1  on the condition of state machine  400  receiving a rising clock edge on clock terminal  406 . To transition from state  3  to state  1 , state machine  400  drives (1) a signal on command bus  402  for selective cycle register  10  to select port  116 A as its input source, (2) a signal on command line  410  for selective shadow register  30  to select port  204 A as its input source, and (3) a signal on command line  412  for selective incrementor  50  to select port  122 A as its input source. The conditions and actions for the transition from state  3  to state  1  are captioned in box  64  of FIG.  4 B. 
     State machine  400  transitions from state  1  to state  4  on the conditions of state machine  400  receiving an active signal on terminal  404  and an active signal on terminal  408 . To transition from state  1  to state  4 , state machine  400  drives (1) a signal on command bus  402  for selective cycle register  10  to select port  114 A as its input source, (2) a signal on command line  410  for selective shadow register  30  to select port  216 A as its input source, and (3) a signal on command line  412  for selective incrementor  50  to select port  124 A as its input source. The conditions and actions for the transition from state  1  to state  4  are captioned in box  73  of FIG.  4 B. 
     State machine  400  transitions from state  4  to state  1  on the condition of state machine receiving an inactive signal on terminal  408 . To transition from state  4  to state  1 , state machine  400  drives (1) a signal on command bus  402  for selective cycle register  10  to select port  116 A as its input source, (2) a signal on command line  410  for selective shadow register  30  to select port  204 A as its input source, and (3) a signal on command line  412  for selective incrementor  50  to select port  122 A as its input source. The conditions and actions for the transition from state  4  to state  1  are captioned in box  74  of FIG.  4 B. 
     FIG. 5A illustrates a low-level block diagram of the embodiment illustrated in FIG.  4 A. As shown, selective cycle register  10  includes a cycle time store  12  and a first multiplexer  14  (“mux  14 ”). Cycle time store  12  includes a clock terminal  108 C, time bus  110 , and a store port  136 . Clock terminal  108 C is coupled to clock terminal  108 B to receive the clock signal from clock line  506 . Cycle time store  12  drives onto time bus  110  the time signal it receives on store port  136  with a one clock delay. Cycle time store  12  is, for example, a register. 
     Mux  14  includes a first time port  102 C, a second time port  104 C, a command port  106 C, a first selective port  116 B, a second selective port  114 B, and a first multiplexer bus  134 , where bus  134  is coupled to port  136  of cycle time store  12 . Thus, mux  14  selects an input source among port  102 C, port  104 C, port  114 C, and port  116 C in accordance to signals received on port  106 C, and outputs the time signal of the input source on bus  134  to port  136  of cycle time store  12 . Port  102 C, port  104 C, port  106 C, port  116 B, and port  114 B are coupled to port  102 B,  104 B, port  106 B, port  116 A, and port  114 A, respectively, and receive the control signal on command bus  402 , the time signal on bus  508  (NEW_TIME), the time signal on bus  502  (MASTER_TIME), the time signal on bus  126  (incremented CYCLE_TIME), and the time signal on bus  110  (frozen CYCLE_TIME). 
     Selective incrementor  50  includes an incrementor  52  and a second multiplexer  54  (“mux  54 ”). Incrementor  52  operates like incrementor  20  and incrementor  40  of FIG.  3 A. Incrementor  52  includes an incrementor port  132  and an incrementor bus  126 . Mux  54  includes a first port  122 B, a second port  124 B, a multiplexer bus  130 , and a command terminal  128 B, where bus  130  is coupled to incrementor port  132 . Thus, mux  54  selects an input source among port  122 B and  124 B in accordance to the signal received on port  128 B, and drives the signal of the input source on bus  130 . Port  122 B, port  124 B, and terminal  128 B are coupled to port  122 A, port  124 A, and terminal  128 A, respectively, and receive the time signals on bus  110  (CYCLE_TIME), the time signal on bus  210  (SHADOW_TIME), and the signal from line  412 . 
     The previously discussed cycle timer modes are now explained in relation to cycle time store  12 , mux  14 , incrementor  52 , and mux  54  of FIG.  5 A. In the first cycle timer mode, cycle timer  100  drives signal CYCLE_TIME on bus  110  at each rising clock edge received on terminal  108 A and then increment signal CYCLE_TIME. To do so, mux  14  selects port  116 B of incrementor  20  as its input source and mux  54  selects port  122 B as its input source. Thus, at each rising clock edge, cycle time store  12  drives onto time bus  110  a time signal it received at the previous rising clock edge at port  136  from incrementor  52 , and incrementor  52  constantly increments the time signal it receives at port  132  from cycle timer store  12  and drives the incremented time signal on bus  126 . 
     In the second cycle timer mode, cycle timer  100  saves a signal NEW_TIME received on port  102 A as signal CYCLE_TIME. To do so, mux  14  selects port  102 C as its input source for one clock cycle, where port  102 C is coupled to the NEW_TIME bus  508  through port  102 B and port  102 A. 
     In the third cycle timer mode, cycle timer  100  saves signal MASTER_TIME received on port  104 A a signal CYCLE_TIME. To do so, mux  14  selects port  104 C as its input source for one clock cycle, where port  104 C is coupled to the MASTER_TIME bus  502  through port  104 B and port  104 A. 
     In the fourth cycle timer mode, cycle timer  100  drives signal CYCLE_TIME on time bus  110  at each rising clock edge received on clock terminal  108 A without incrementing signal CYCLE_TIME. To do so, mux  14  selects port  114 B as its input source, where port  114 B is coupled to time output bus  110  through port  114 A. The above operation modes cycle timer  100  are controlled by signals from state machine  400  received on port  106 C of mux  14  and  128 B of mux  54  in accordance to the state diagram illustrated in the to be described FIG.  5 B. 
     Selective shadow register  30  includes shadow time store  32  and a third multiplexer  34  (“mux  34 ”). Shadow time store  32  includes a shadow timer clock input terminal  208 C, time bus  210 , and a time input port  220 . Shadow time store  32  drives onto time bus  210  the signal it receives on port  220  with a one clock delay. Shadow time store  32  is, for example, a register. 
     Mux  34  includes a time port  204 C, a command terminal  206 C, a time port  216 B, and a time bus  218 , where bus  218  is coupled to port  220  of shadow time store  32 . Thus, mux  34  can select an input source from port  204 C and port  216 B, and output the signal received from the input source on bus  218 . Port  204 C, terminal  206 C, and port  216 B are coupled to port  204 B, terminal  206 B, and port  216 A, respectively, and receive the time signal (MASTER_TIME) on bus  502 , the signal on line  410 , and the time signal (incremented SHADOW_TIME) on bus  126 . 
     The previously discussed shadow timer modes are now explained in relation to shadow time store  32 , mux  34 , incrementor  52 , and mux  54  of FIG.  5 A. In the first shadow timer mode, shadow timer  200  saves signal MASTER_TIME received on port  204 A as the SHADOW_TIME signal and drives the SHADOW_TIME signal on time bus  210  at each rising clock edge received on clock terminal  208 A. To do so, mux  34  selects port  204 C as its input source, where port  204 C is coupled to MASTER_TIME bus  502  through port  204 B and port  204 A. 
     In the second shadow timer mode, shadow timer  200  drives the SHADOW_TIME signal on time bus  210  at each rising clock edge received terminal  208 A and then increments the SHADOW_TIME signal. To do so, mux  34  selects port  216 B as its input source and mux  54  selects port  124 B as its input source. Thus, at each rising clock edge, shadow time store  32  drives a time signal on bus  210  it received at the previous rising clock edge at port  220  from incrementor  52 , and incrementor  52  constantly increments the time signal it receives at port  132  from shadow time store  32  and drives the incremented time signal on bus  126 . The above operation modes of shadow timer  200  are controlled through signals received from state machine  400  on terminal  206 C of mux  34  and terminal  128 B of mux  54  in accordance to the state diagram illustrated in the to be described FIG.  5 B. Appendix A contains microfiche of VERILOG source code implementing state machine  400  illustrated in FIG.  5 A. 
     FIG. 5B illustrates a state diagram for the embodiment illustrated in FIG.  5 A. State machine  400  starts in state  0  (“zero state”). State machine  400  transitions from state  0  to state  1  on the condition of state machine  400  receiving a rising clock edge on clock terminal  406 . To transition from state  0  to state  1  (“normal state”), state machine  400  drives (1) a signal on command bus  402  for mux  14  to select port  116 B, (2) a signal on command line  412  for mux  34  to select port  204 C, and (3) a signal on command line  410  for mux  54  to select port  122 B. The conditions and actions for the transition from state  0  to state  1  are captioned in box  33  of FIG.  5 B. 
     State machine  400  transitions from state  1  to state  2  (“load state”) on the condition of state machine  400  receiving an active signal on terminal  407 . To transition from state  1  to state  2 , state machine  400  drives a signal on command bus  402  for mux  14  to select port  102 C. The actions of mux  34  and mux  54  are irrelevant in the transition from state  1  to state  2 . The conditions and actions for the transition from state  1  to state  2  are captioned in box  55  of FIG.  5 B. 
     State machine  400  transitions from state  2  to state  1  on the condition of state machine  400  receiving a rising clock edge on terminal  406 . To transition from state  2  to state  1 , state machine  400  drives (1) a signal on command bus  402  for mux  14  to select port  116 B, (2) a signal on command line  412  for mux  34  to select port  204 C, and (3) a signal on command line  410  for mux  54  to select port  122 B. The conditions and actions for the transition from state  2  to state  1  are captioned in box  56  of FIG.  5 B. 
     State machine  400  transitions from state  1  to state  3  (“update state”) on the conditions of state machine  400  receiving of an active signal on terminal  404  and an inactive signal on terminal  408 . In a first implementation, to transition from state  1  to state  3 , state machine  400  drives a signal on command bus  402  for mux  14  to select port  104 C. The actions of mux  34  and mux  54  are irrelevant in the transition from state  1  to state  3  of the first implementation. The actions for the first implementation are captioned in box  65  of FIG.  5 B. 
     In a second implementation, to transition from state  1  to state  3 , state machine  400  drives (1) a signal on command bus  402  for mux  14  to select port  116 B, (2) a signal on command line  410  for mux  34  to select port  204 C, and (3) a signal on command line  412  for mux  54  to select port  124 B. The actions for the second implementation are captioned in box  67  of FIG.  5 B. As configured, incrementor  52  increments the SHADOW_TIME signal, which is equal to signal MASTER_TIME, and drives the incremented SHADOW_TIME signal to cycle time store  12  to avoid a one clock delay caused by the first implementation. Both the first implementation and the second implementation share the same conditions for the transition from state  1  to state  3 , which are captioned in both box  65  and box  67  of FIG.  5 B. 
     State machine  400  transitions from state  3  to state  1  on the condition of state machine  400  receiving a rising clock edge on clock terminal  406 . To transition from state  3  to state  1 , state machine  400  drives (1) a signal on command bus  402  for mux  14  to select port  116 B, (2) a signal on command line  412  for mux  34  to select port  204 C, and (3) a signal on command line  410  for mux  54  to select port  122 B. The conditions and actions for the transition from state  3  to state  1  are captioned in box  66  of FIG.  5 B. 
     State machine  400  transitions from state  1  to state  4  on the conditions of state machine  400  receiving an active signal on terminal  404  and an active signal on terminal  408 . To transition from state  1  to state  4 , state machine  400  drives (1) a signal on command bus  402  for mux  14  to select port  114 B, (2) a signal on command line  412  for mux  34  to select port  216 B, and (3) a signal on command line  410  for mux  54  to select port  124 B. The conditions and actions for the transition from state  1  to state  4  are captioned in box  75  of FIG.  5 B. 
     State machine  400  transitions from state  4  to state  1  on the condition of state machine receiving an inactive signal on terminal  408 . To transition from state  4  to state  1 , state machine  400  drives (1) a signal on command bus  402  for mux  14  to select port  1116 B, (2) a signal on command line  412  for mux  34  to select port  204 C, and (3) a signal on command line  410  for mux  54  to select port  122 B. The conditions and actions for the transition from state  4  to state  1  are captioned in box  76  of FIG.  5 B. 
     Numerous modifications and adaptations of the embodiments described herein will be apparent to the skilled artisan in view of the disclosure. For example, state machine  400  may be configured differently to achieve the same or similar results. Specifically, FIG. 5B may be modified so that state  4  transitions to a state  5  on the condition of an inactive signal on terminal  408 . To transition from state  4  to state  5 , state machine  400  commands mux  14  to select port  104 C as its input source. State  5  then transitions to state  1  on the condition of a rising clock edge on terminal  406 . To transition from state  5  to state  1 , state machine  400  commands (1) mux  14  to select port  116 B, (2) mux  34  to select port  204 C, and (3) mux  54  to select port  122 B. Numerous such changes and modifications are encompassed by the attached claims. 
     
       
         
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
               
             
               
               
               
               
             
               
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
             
           
               
                 APPENDIX A 
               
               
                   
               
             
             
               
                 /************************************************************************** 
               
               
                 # CORE:  1394 Device Controller (1394DC) 
               
               
                 # MODULE:  cycmon 
               
               
                 # TOP MODULE:  llc (Link Layer Core) 
               
               
                 # CLOCKS: Clk 
               
               
                 # RESETS: Rst (Synchronous Active High) 
               
               
                 # FLIPFLOP COUNT: 35 
               
               
                 **************************************************************************/ 
               
               
                 ′timescale 1 ns/1 ns 
               
               
                 module cw6000_llccycmon( 
               
             
          
           
               
                   
                 phy_sclkp, 
               
             
          
           
               
                 // 
                 cycmon_sclkp, 
               
             
          
           
               
                   
                 i_sresetp, 
               
               
                   
                 clk8kinp, 
               
               
                   
                 gscan_enablep, 
               
               
                   
                 i_aint_writep, 
               
               
                   
                 i_aint_addrp, 
               
               
                   
                 i_aint_wrdatap, 
               
               
                   
                 phyif_subact_gapp, 
               
               
                   
                 phyif_phy_resetp, 
               
               
                   
                 rx_cyclesynchn, 
               
               
                   
                 rx_cycletmrp, 
               
               
                   
                 tx_cycstrtdnn, 
               
               
                   
                 llcreg_cmstrp, 
               
               
                   
                 llcreg_cyctmrenp, 
               
               
                   
                 llcreg_offmatchp, 
               
               
                   
                 llcreg_extcycp, 
               
               
                   
                 cyc_reqn, 
               
               
                   
                 cyc_cycletmrp, 
               
               
                   
                 cyc_125usticp, 
               
               
                   
                 cyc_clk8koutp, 
               
               
                   
                 cyc_set_cyclostp, 
               
               
                   
                 cyc_set_cyctlp, 
               
               
                   
                 cyc_set_cycsecp, 
               
               
                   
                 cyc_set_cycstp, 
               
               
                   
                 cyc_set_cycdnp, 
               
               
                   
                 cyc_set_cycpndp, 
               
               
                   
                 cyc_isophasep 
               
               
                   
                 ); 
               
             
          
           
               
                 // 
                 Port Declarations 
               
               
                 // 
                 Clock and Reset Inputs 
               
             
          
           
               
                   
                 input 
                 phy_sclkp; 
                 // Clock 
               
             
          
           
               
                   
                 input 
                 i_sresetp; 
                 // System Reset 
               
             
          
           
               
                   
                 input 
                 clk8kinp; 
                 // 8000 clk 
               
               
                   
                 input 
                 gscan_enablep; 
               
             
          
           
               
                 // 
                 Application Interface Inputs 
               
             
          
           
               
                   
                 input i_aint_writep; 
               
               
                   
                 input [7:13] i_aint_addrp; 
               
               
                   
                 input [0:31] i_aint_wrdatap; 
               
             
          
           
               
                 // 
                 PHYIF inputs 
               
             
          
           
               
                   
                 input phyif_subact_gapp, 
               
             
          
           
               
                   
                 phyif_phy_resetp; 
               
             
          
           
               
                 // 
                 Transmitter Inputs 
               
             
          
           
               
                   
                 input 
                 tx_cycstrtdnn; // Indicates that the Transmiter sent the cycle 
               
             
          
           
               
                   
                 // 
                 Start packet 
               
               
                   
                 // 
                 CSU Inputs 
               
             
          
           
               
                   
                 input 
                 llcreg_cmstrp; // Indicates that current node is cycle master 
               
               
                   
                 input 
                 llcreg_cyctmrenp; // Indicates that the cycle timer is enabled. 
               
             
          
           
               
                   
                 input [0:11] llcreg_offmatchp; 
               
             
          
           
               
                   
                 input 
                 llcreg_extcycp; 
               
             
          
           
               
                 // 
                 Receiver Inputs 
               
             
          
           
               
                 input 
                 rx_cyclesynchn;// Cycle Start Recieved Indication 
               
             
          
           
               
                 input [0:31] rx_cycletmrp; // Cycle Timer value Received 
               
             
          
           
               
                 // 
                 Outputs 
               
             
          
           
               
                 //  output 
                 cycmon_sclkp; 
               
             
          
           
               
                 output 
                 cyc_reqn; // Request to Transmiter to send the cycle start 
               
             
          
           
               
                 output [0:31] cyc_cycletmrp; // Cycle Timer Value 
               
             
          
           
               
                 output 
                 cyc_125usticp; // Indicates the 125 us reached? 
               
               
                 output 
                 cyc_set_cycsecp; // Indicates the Second Count is incremented 
               
               
                 output 
                 cyc_set_cyclostp; // Indicates the monitor detected a missing 
               
             
          
           
               
                   
                 // cycle start packet 
               
             
          
           
               
                 output 
                 cyc_clk8koutp; 
               
             
          
           
               
                 output 
                 cyc_set_cyctlp,//Set cycle too long intenrupt if cmstr &amp; after 
               
             
          
           
               
                   
                 //transmitting cycle start a subaction gap or 
               
               
                   
                 //bus reset is not detected within 116 uS. 
               
             
          
           
               
                   
                 cyc_set_cycstp,//Set Cycle start intenupt when cycle start 
               
             
          
           
               
                   
                 // packet has been sent or received 
               
             
          
           
               
                   
                 cyc_set_cycdnp,//Set cycle done interrupt indicating arbitration 
               
             
          
           
               
                   
                 // gap has been detected after the cycle start 
               
               
                   
                 // packet. Indicates isochronous cycle is over 
               
             
          
           
               
                   
                 cyc_set_cycpndp,//Set cycle pending interrupt when the cycle 
               
             
          
           
               
                   
                 //count is incremented 
               
             
          
           
               
                   
                 cyc_isophasep; //asserted during isochronous phase 
               
             
          
           
               
                   
                 parameter FF_DELAY = 1; 
               
             
          
           
               
                 // 
                 output register declarations 
               
             
          
           
               
                   
                 reg 
                 cyc_set_cyctlp, 
               
             
          
           
               
                   
                 cyc_set_cycstp, 
               
               
                   
                 cyc_set_cycdnp, 
               
               
                   
                 cyc_isophasep; 
               
             
          
           
               
                 reg 
                 cyc_reqn; 
               
             
          
           
               
                 wire [0:31] cyc_cycletmrp; 
               
             
          
           
               
                 reg 
                 cyc_set_cyclostp; 
               
               
                 reg 
                 cyc_set_cycpndp, 
               
             
          
           
               
                   
                 cyc_125usticp; 
               
             
          
           
               
                 reg 
                 cyc_set_cycsecp; 
               
             
          
           
               
                 // 
                 Local Declarations 
               
             
          
           
               
                   
                 wire [0:31] catchup_regp; 
               
               
                   
                 reg [0:6] catchup_seccntp; 
               
               
                   
                 reg [0:12] catchup_cyccntp; 
               
               
                   
                 reg [0:11] catchup_cycoffp; 
               
             
          
           
               
                 reg [0:11] Cycle_Offset;  // Cycle Offset register 
               
               
                 reg [0:12] Cycle_Count;  // Cycle Count register 
               
               
                 reg [0:6] Second_Count;  // Second Count register 
               
             
          
           
               
                   
                 reg [0:12] cyctlcntp; 
               
             
          
           
               
                   
                 reg 
                 cyctlcntenp; 
               
             
          
           
               
                 reg 
                 offset_incr;  // Toggling flag to increment Offset 
               
             
          
           
               
                   
                 wire 
                 cyc_offset_carry; // Indication of 125us. 
               
               
                   
                 wire 
                 catch_off_carryp; 
               
               
                   
                 wire 
                 catch_cyccnt_carryp; 
               
             
          
           
               
                   
                 wire cpuwritep, 
               
             
          
           
               
                 // 
                 forwardp, 
               
             
          
           
               
                   
                 load_cycsyncp; 
               
             
          
           
               
                   
                 wire [0:11] cycoff_incrmtrp; 
               
               
                   
                 wire [0:6] seccnt_incmtrp; 
               
               
                   
                 wirc [0:12] cyccnt_incrmtrp; 
               
               
                   
                 reg clk8kin_synclp, 
               
             
          
           
               
                   
                 clk8kin_syncedp, 
               
               
                   
                 clk8kin_sync_dlyp, 
               
               
                   
                 clk8kin_sync_dly2p; 
               
             
          
           
               
                   
                 wire clk8k_risep; 
               
             
          
           
               
                   
                 wire 
                 clk8kmtchp; 
               
               
                   
                 wire 
                  cyc_clk8koutp; 
               
               
                   
                 reg 
                 clk8koutp; 
               
             
          
           
               
                 wire 
                  cyc_count_carry; // Indication of 1sec. 
               
               
                 reg 
                 exp_cycle_synch; // indicates that cycle synch event is pendg 
               
               
                 reg 
                 cyctmrcntenp; 
               
             
          
           
               
                 ‘define CYC_MOD_8000  13′h1F3F // Cycle Count 
               
               
                 ‘define CYC_MOD_127  7′h7F // Second Count 
               
               
                 ‘define CYC_TL_116  13′h16a8 //116us = 5800 cycles 
               
               
                 /*cw6000_ckbufc cycgckbufi(.bclkp(cycmon_sclkp), 
               
             
          
           
               
                   
                 .pclkp(phy_sclkp)); 
               
             
          
           
               
                 */ 
               
               
                 //isochronous cycle detection 
               
               
                 //always @ posedge cycmon_sclkp) begin 
               
               
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 casez){i_sresetp,rx_cyclesynchn,tx_cycstrtdnn,phyif_subact_gapp,phyif_phy_resetp})//synopsys parallel_case 
               
             
          
           
               
                   
                 5′b1????:cyc_isophasep &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 5′b00??? : cyc_isophasep &lt;= #FF_DELAY 1′b1; 
               
               
                   
                 5′b0?0?? : cyc_isophasep &lt;= #FF_DELAY 1′b1; 
               
               
                   
                 5′b0111? : cyc_isophasep &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 5′b011?1 : cyc_isophasep &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 5′b01100 : cyc_isophasep &lt;= #FF_DELAY cyc_isophasep; 
               
               
                   
                 default : cyc_isophasep &lt;= #FF_DELAY 1′bx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,rx_cyclesynchn,tx_cycstrtdnn,phyif_arb_gapp,phyif_subact_gapp}) 
               
             
          
           
               
                 end // always @ (posedge phy_sclkp) 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) begin 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 cyc_set_cycstp &lt;= #FF_DELAY i_sresetp ? 1′b0: 
               
             
          
           
               
                   
                 (˜rx_cyclesynchn | ˜tx_cycstrtdnn); 
               
             
          
           
               
                 /* 
                 if(_sresetp) cyc_set_cycstp &lt;= #FF_DELAY 1′b0; 
               
             
          
           
               
                   
                 else if (˜i_sresetp) cyc_set_cycstp &lt;= #FF_DELAY ˜rx_cyclesynchn | ˜tx_cycstrtdnn; 
               
               
                   
                 else cyc_set_cycstp &lt;= #FF_DELAY 1′bx; 
               
             
          
           
               
                 */ 
               
             
          
           
               
                   
                 end // always @ (posedge phy_sclkp) 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) begin 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 cyc_set_cycdnp &lt;= #FF_DELAY i_sresetp ? 1′b0 : (cyc_isophasep &amp; 
               
             
          
           
               
                   
                 (phyif_subact_gapp | 
               
               
                   
                 phyif_phy_resetp)); 
               
             
          
           
               
                 /* 
                 if(_sresetp) cyc_set_cycdnp &lt;= #FF_DELAY 1′b0; 
               
             
          
           
               
                   
                 else if(˜i_sresetp) cyc_set_cycdnp &lt;= #FF_DELAY cyc_isophasep &amp; 
               
             
          
           
               
                   
                 (phyif_subact_gapp | 
               
               
                   
                 phyif_phy_resetp); 
               
             
          
           
               
                   
                 else cyc_set_cycdnp &lt;= #FF_DELAY 1′bx; 
               
             
          
           
               
                 */ 
                 end // always @ (posedge phy_sclkp) 
               
             
          
           
               
                   
                 //Cycle too long detection 
               
               
                   
                 //cyc too long if 116 us has passed after cycle start was sent and 
               
               
                   
                 //arbitration reset gap or subaction gap has not been detected 
               
               
                   
                 //enable clock to cyctl counter only if 
               
             
          
           
               
                 /* 
                 cw6000_gckand2b cyctlpgck(.gclkp( cyctlpclkp), 
               
             
          
           
               
                   
                 .pclkp( phy_sclkp), 
               
               
                   
                 .gaten( ˜i_sresetp | 
               
             
          
           
               
                   
                 ˜tx_cycstrtdnn | 
               
               
                   
                 cyctlcntenp)), 
               
             
          
           
               
                   
                 .gscan_enablep( gscan_enablep) 
               
               
                   
                 ); 
               
             
          
           
               
                 */ 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) begin 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 if (i_sresetp) cyc_set_cyctlp &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 else if (˜i_sresetp) cyc_set_cyctlp &lt;= #FF_DELAY ˜(|cyctlcntp[0:12]); 
               
               
                   
                 else cyc_set_cyctlp &lt;= #FF_DELAY 1′bx; 
               
             
          
           
               
                   
                 end // always @ (posedge phy_sclkp) 
               
             
          
           
               
                 /* 
                 always @ (posedge cyctlpclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,tx_cycstrtdnn})//synopsys parallel_case 
               
             
          
           
               
                   
                 2′b1? : cyctlcntp[0:12] &lt;= #FF_DELAY ‘CYC_TL_116;//116 us 
               
               
                   
                 2′b00 : cyctlcntp[0:12] &lt;= #FF_DELAY ‘CYC_TL_116;//116 us 
               
               
                   
                 2′b01 : cyctlcntp[0:12] &lt;= #FF_DELAY cyctlcntp[0:12] - 1′b1; 
               
               
                   
                 default: cyctlcntp[0:12] &lt;= #FF_DELAY 13′hxxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,txcycstrtdnn}) 
               
             
          
           
               
                   
                 end // always @ (posedge cyctlpclkp) 
               
             
          
           
               
                 */ 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,tx_cycstrtdnn,cyctlcntenp})//synopsys parallel_case 
               
             
          
           
               
                   
                 3′b1?? : cyctlcntp[0:12] &lt;= #FF_DELAY ‘CYC_TL_116;//116 us 
               
               
                   
                 3′b00? : cyctlcntp[0:12] &lt;= #FF_DELAY ‘CYC_TL_116;//116 us 
               
               
                   
                 3′b011 : cyctlcntp[0:12] &lt;= #FF_DELAY cyctlcntp[0:12] - 1′b1; 
               
               
                   
                 3′b010 : cyctlcntp[0:12] &lt;= #FF_DELAY cyctlcntp[0:12]; 
               
               
                   
                 default: cyctlcntp[0:12] &lt;= #FF_DELAY 13′hxxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,txcycstrtdnn}) 
               
             
          
           
               
                   
                 end // always @ (posedge cyctlpclkp) 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) begin 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 casez ({i_sresetp,tx_cycstrtdnn,phyif_phy_resetp, 
               
             
          
           
               
                   
                 phyif_subact_gapp,˜(|cyctlcntp[0:12]),llcreg_cyctmrenp})//synopsys parallel_case 
               
             
          
           
               
                   
                 6′b1????? : cyctlcntenp &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 6′b0????0 : cyctlcntenp &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 6′b00???1 : cyctlcntenp &lt;=#FF_DELAY 1′b1; 
               
               
                   
                 6′b011??1 : cyctlcntcnp &lt;=#FF_DELAY 1′b0; 
               
               
                   
                 6′b01?1?1 : cyctlcntenp &lt;=#FF_DELAY 1′b0; 
               
               
                   
                 6′b01??11 : cyctlcntenp &lt;=#FF_DELAY 1′b0; 
               
               
                   
                 6′b010001 : cyctlcntenp &lt;=#FF_DELAY cyctlcntenp; 
               
               
                   
                 default: cyctlcntenp &lt;=#FF_DELAY 1′bx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,tx_cycstrtdnn,phyif_arb_gapp,phyif_subact_gapp}) 
               
             
          
           
               
                   
                 end // always @ (posedge phy_sclkp) 
               
             
          
           
               
                   
                 // 
                 Output cycle timer value generation 
               
             
          
           
               
                   
                 assign cyc_cycletmrp = {Second_Count, Cycle_Count, Cycle_Offset}; 
               
               
                   
                 assign catchup_regp = {catchup_seccntp, catchup_cyccntp, catchup_cycoffp}; 
               
             
          
           
               
                   
                 // 
                 synopsys sync_set_reset “i_sresetp” 
               
               
                   
                 // 
                 Generation of offset incrementer strobe by toggling 
               
               
                   
                 // 
                 this flag every clock. This will control the cycle offset 
               
               
                   
                 // 
                 incrementing every other clock 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) begin 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,llcreg_cyctmrenp})//synopsys parallel_case 
               
             
          
           
               
                   
                 2′b1? : offset_incr &lt;=#FF_DELAY 1′b0; 
               
               
                   
                 2′b01 : offset_incr &lt;=#FF_DELAY ˜offset_incr; 
               
               
                   
                 2′b00 : offset_incr &lt;=#FF DELAY 1′b0; 
               
               
                   
                 default : offset_incr &lt;=#FF_DELAY 1′bx; 
               
             
          
           
               
                   
                 endcase // casez(i_sresetp,llcreg_cyctmrenp) 
               
             
          
           
               
                 /* 
                 if(i_sresetp) offset_incr &lt;=#FF_DELAY 1′b0; 
               
             
          
           
               
                   
                 else if (˜i_sresetp &amp; llcreg_cyctmrenp) offset_incr &lt;=#FF_DELAY ˜offset_incr; 
               
               
                   
                 else if(˜i_sresetp &amp; llcreg_cyctmrenp) offset_incr &lt;=#FF_DELAY 1′b0; 
               
               
                   
                 else offset_incr &lt;=#FF_DELAY 1′bx; 
               
             
          
           
               
                 */ 
               
             
          
           
               
                   
                 end 
               
               
                   
                 //toggle clk8kout when cycle_offset matches 1/2 of offmatchp value and 
               
               
                   
                 //when cycle_offset matches offmatch value 
               
             
          
           
               
                 /*bug50*/ 
               
             
          
           
               
                   
                 assign clk8kmtchp = ((Cycle_Offset[0:11] == {1′b0,llcreg_offmatchp[0:10]}) 
               
             
          
           
               
                   
                 &amp; offset_incr) | cyc_offset_carry; 
               
             
          
           
               
                 /* 
                 assign clk8kmtchp = ((cycoff_incrmtrp[0:11] == 
               
             
          
           
               
                   
                 {1′b0,llcreg_offmatchp[0:10]}) 
               
               
                   
                 &amp; offset_incr)| 
               
               
                   
                 (˜cyctmrcntenp ? catch_off_carryp : cyc_offset_carry); 
               
             
          
           
               
                 */ 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) begin 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                 /*bug58 
                 casez({i_sresetp,clk8kmtchp}) 
               
             
          
           
               
                   
                 2′b1? : clk8koutp &lt;=#FF_DELAY 1′b0; 
               
               
                   
                 2′b01 : clk8koutp &lt;= #FF_DELAY ˜clk8koutp; 
               
               
                   
                 2′b00 : clk8koutp &lt;=#FF_DELAY clk8koutp; 
               
             
          
           
               
                 */ 
               
             
          
           
               
                   
                 casez({i_sresetp,clk8kmtchp,cyctmrcntenp}) 
               
             
          
           
               
                   
                 3′b1?? : clk8koutp &lt;=#FF_DELAY 1′b0; 
               
               
                   
                 3′b011 : clk8koutp &lt;=#FF_DELAY ˜clk8koutp; 
               
               
                   
                 3′b001 : clk8koutp &lt;=#FF_DELAY clk8koutp; 
               
               
                   
                 3′b0?0 : clk8koutp &lt;=#FF_DELAY clk8koutp; 
               
               
                   
                 default : clk8koutp &lt;=#FF_DELAY 1′bx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,clk8kmtchp}) 
               
             
          
           
               
                   
                 end // always @ (posedge phy_sclkp) 
               
               
                   
                 assign cyc_clk8koutp = (llcreg_cmstrp &amp; llcreg_extcycp) ? clk8kin_syncedp: 
               
             
          
           
               
                   
                 clk8koutp; 
               
             
          
           
               
                   
                 assign cyc_offset_carry = ˜(llcreg_cmstrp &amp; llcreg_extcycp) ? 
               
             
          
           
               
                   
                 //cmstr is not set or extcyc is not set 
               
               
                   
                 (cyctmrcntenp &amp; 
               
               
                   
                 (Cycle_Offset ==llcreg_offmatchp) &amp; offset_incr) 
               
               
                   
                 : 
               
               
                   
                 //extcyc set and cmstr set 
               
               
                   
                 ctk8k_risep &amp; offset_incr; 
               
             
          
           
               
                   
                 assign catch_off_carryp = (llcreg_cmstrp &amp; llcreg_extcycp) ? 
               
             
          
           
               
                   
                 ((catchup_cycoffp == llcreg__offmatchp) &amp; 
               
               
                   
                 offset_incr) 
               
               
                   
                 clk8k_risep &amp; offset_incr; 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) 
               
             
          
           
               
                   
                 casez({i_sresetp,llcreg_cmstrp, 
               
             
          
           
               
                   
                 (˜rx_cyclesynchn &amp; (cyc_cycletmrp[0:31] &gt; rx_cycletmrp[0:31])), 
               
             
          
           
               
                 //bug52 
                 (˜cyctmrcntenp &amp; (cyc_cycletmrp[0:31] == catchup_regp[0:31]))} 
               
               
                   
                 ((˜cyctmrcntenp &amp; (cyc_cycletmrp[0:31] == catchup_regp[0:31])) | 
               
               
                   
                 cpuwritep) 
               
               
                   
                 } 
               
             
          
           
               
                   
                 )//synopsys parallel_case 
               
             
          
           
               
                   
                 4′b1??? : cyctmrcntenp &lt;= #FF_DELAY 1′b1; 
               
               
                   
                 4′b01?? : cyctmrcntenp &lt;=#FF_DELAY 1′b1; 
               
               
                   
                 4′b001? : cyctmrcntenp &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 4′b0001 : cyctmrcntenp &lt;= #FF_DELAY 1′b1; 
               
               
                   
                 4′b0000 : cyctmrcntenp &lt;= #FF_DELAY cyctmrcntenp; 
               
               
                   
                 default : cyctmrcntenp &lt;= #FF_DELAY 1′bx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp, . . . 
               
               
                   
                 assign cpuwritep = i_aint_writep &amp; (i_aint_addrp[7:13] == 7′h01); 
               
             
          
           
               
                 // 
                 assign forwardp = (cyc_cycletmrp[0:31] &gt;= catchup_regp[0:31]); 
               
             
          
           
               
                   
                 //(assign forwardp = (cyc_cycletmrp[0:31] &lt; rx_cyctetmrp[0:31]); 
               
               
                   
                 assign load_cycsyncp = ˜rx_cyclesynchn &amp; 
               
             
          
           
               
                   
                 (cyc_cycletmrp[0:31] &lt;= rx_cycletmrp[0:31]); 
               
             
          
           
               
                   
                 assign cycoff_incrmtrp[0:11] = (˜cyctmrcntenp ? 
               
             
          
           
               
                   
                 catchup_cycofp[0:11]: 
               
               
                   
                 Cycle_Offset[0:11]) + 1′b1; 
               
             
          
           
               
                 /* 
                 cw6000_gckand2c catchupgck(.gclkp( catchupclkp), 
               
             
          
           
               
                   
                 .pclkp( phy_sclkp), 
               
               
                   
                 .gaten( ˜i_sresetp | 
               
             
          
           
               
                   
                 ((˜rx_cyclesynchn | 
               
               
                   
                 (˜cyctmrcntenp &amp; offset_incr)) &amp; 
               
               
                   
                 llcreg_cyctmrenp)) ), 
               
             
          
           
               
                   
                 .gscan_enablep( gscan_enablep ) 
               
               
                   
                 ); 
               
             
          
           
               
                 */ 
               
             
          
           
               
                 /* 
                 always @ (posedge catchupclkp) begin 
               
               
                   
                 casez({i_sresetp,rx_cyclesynchn,catch_off_carryp})//synopsys parallel_case 
               
             
          
           
               
                   
                 3′b1?? : catchup_cycoffp[0:11] &lt;= #FF_DELAY 12′h000; 
               
               
                   
                 3′b00? : catchup_cycoffp[0:11] &lt;= #FF_DELAY rx_cycletmtp[20:31]; 
               
               
                   
                 3′b010 : catchup_cycoffp[0:11] &lt;= #FF_DELAY cycoff_incrmtrp[0:11]; 
               
               
                   
                 3′b011 : catchup_cycoffp[0:11] &lt;= #FF_DELAY 12′h000;//wrap 
               
               
                   
                 default : catchup_cycoffp[0:11] &lt;= #FF_DELAY 12′hxxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,cpuwritep,rx_cyclesynchn,forwardp}) 
               
             
          
           
               
                   
                 end // always @ (posedge catchupclkp) 
               
             
          
           
               
                 */ 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,rx_cyclesynchn,catch_off_carryp,cyctmrcntenp,offset_incr,llcreg_cyctmrenp})//synopsys parallel_case 
               
             
          
           
               
                   
                 6′b1????? : catchup_cycoffp[0:11] &lt;= #FF_DELAY 12′h000; 
               
               
                   
                 6′b0????0 : catchup_cycoffp[0:11] &lt;= #FF_DELAY catchup_cycoffp[0:11]; 
               
               
                   
                 6′b00???1 : catchup_cycoffp[0:11] &lt;= #FF_DELAY rx_cycletmrp[20:31]; 
               
               
                   
                 6′b010011 : catchup_cycoffp[0:11] &lt;= #FF_DELAY cycoff_incrmtrp[0:11]; 
               
               
                   
                 6′b011011 : catchup_cycoffp[0:11] &lt;= #FF_DELAY 12′h000;//wrap 
               
               
                   
                 6′b01??01 : catchup_cycoffp[0:11] &lt;= #FF_DELAY catchup_cycoffp[0:11]; 
               
               
                   
                 6′b01?111 : catchup_cycoffp[0:11] &lt;= #FF_DELAY catchup_cycoffp[0:11]; 
               
               
                   
                 default: catchup_cycoffp[0:11] &lt;= #FF_DELAY 12′hxxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,cpuwritep,rx_cyclesynchn,forwardp}) 
               
             
          
           
               
                   
                 end // always @ (posedge catchupclkp) 
               
             
          
           
               
                 /* 
                 always @ (posedge catchupclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,rx_cyclesynchn,catch_cyccnt_carryp, 
               
             
          
           
               
                   
                 catch_off_carryp})//synopsys parallel_case 
               
             
          
           
               
                   
                 4′b1??? : catchup_cyccntp[0:12] &lt;= #FF_DELAY 13′h0000; 
               
               
                   
                 4′b00?? : catchup_cyccntp[0:12] &lt;= #FF_DELAY rx_cycletmrp[7:19]; 
               
               
                   
                 4′b0100 : catchup_cyccntp[0:12] &lt;= #FF_DELAY catchup_cyecntp[0:12]; 
               
               
                   
                 4′b0101 : catchup_cyccntp[0:12] &lt;= #FF_DELAY cyccnt_incrmtrp[0:12]; 
               
               
                   
                 4′b011? : catchup_cyccntp[0:12] &lt;= #FF_DELAY 13′h0000;//wrap 
               
               
                   
                 default: catchup_cyccntp[0:12] &lt;= #FF_DELAY 13′hxxxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,cpuwritep,rx_cyclesynchn,forwardp}) 
               
               
                   
                 end // always @ (posedge catchupclkp) 
               
             
          
           
               
                 */ 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 casez({i_resetp,rx_cyclesynchn,catch_cyccnt_carryp, 
               
             
          
           
               
                   
                 catch_off_carryp,llcreg_cyctmrenp})//synopsys parallel_case 
               
             
          
           
               
                   
                 5′b1???? : catchup_cyccntp[0:12] &lt;= #FF_DELAY 13′h0000; 
               
               
                   
                 5′b0???0 : catchup_cyccntp[0:12] &lt;= #FF_DELAY catchup_cyccntp[0:12]; 
               
               
                   
                 5′b00??1 : catchup_cyccntp[0:12] &lt;= #FF_DELAY rx_cycletmrp[7:19]; 
               
               
                   
                 5′b01001 : catchup_cyccntp[0:12] &lt;= #FF_DELAY catchup_cyccntp[0:12]; 
               
               
                   
                 5′b01011 : catchup_cyccntp[0:12] &lt;= #FF_DELAY cyccnt_incrmtrp[0:12]; 
               
               
                   
                 5′b011?1 : catchup_cyccntp[0:12] &lt;= #FF_DELAY 13′h0000;//wrap 
               
               
                   
                 default: catchup_cyccntp[0:12] &lt;= #FF_DELAY 13′hxxxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,cpuwritep,rx_cyclesynchn,forwardp}) 
               
             
          
           
               
                   
                 end // always @ (posedge catchupclkp) 
               
             
          
           
               
                   
                 // 
                 Cycle Offset Implementation 
               
             
          
           
               
                 /* 
                 cw6000_gckand2c cyctmrgck(.gclkp( cyctmrclkp), 
               
             
          
           
               
                   
                 .pclkp( phy_sctkp ), 
               
               
                   
                 .gaten( ˜(i_sresetp | 
               
             
          
           
               
                   
                 ((load_cycsyncp | cpuwritep | 
               
             
          
           
               
                   
                 (cyctmrcntenp &amp; offset_incr)) 
               
               
                   
                 &amp; llcreg_cyctmrenp)) ), 
               
             
          
           
               
                   
                 .gscan_enablep( gscan_enablep) 
               
               
                   
                 ); 
               
             
          
           
               
                 */ 
               
             
          
           
               
                 /* 
                 always _(posedge cyctrnrclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,load_cycsyncp,cpuwritep,cyc_offset_carry})//synopsys parallel_case 
               
             
          
           
               
                   
                 4′b1??? : Cycle_Offset &lt;= #FF_DELAY 12′h000; 
               
               
                   
                 4′b010? : Cycle_Offset &lt;= #FF_DELAY __cycletmrp[20:31]; //cycle synch write 
               
               
                   
                 4′b0?1? : Cycle_Offset &lt;= #FF_DELAY i_aint_wrdatap[20:31]; //cpu write has priority 
               
             
          
           
               
                   
                 4′b0001 : Cycle_Offset &lt;= #FF_DELAY 12′h000; 
               
             
          
           
               
                   
                 4′b0000 : Cycle_Offset &lt;= #FF_DELAY cycoff_incrmtrp[0:11]; 
               
               
                   
                 default : Cycle_OffSet &lt;= #FF_DELAY 12′hxxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,load_cycsyncp,cpuwritep_cyc_offset_carry}) 
               
             
          
           
               
                   
                 end // always @ (posedge phy_sclkp) 
               
             
          
           
               
                 */ 
               
             
          
           
               
                   
                 always _(posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,load_cycsyncp,cpuwritep,cyc_offset_carry,cyctmrcntemp,offset_incr,llcreg_cyctmrenp})//synopsys 
               
             
          
           
               
                 parallel_case 
               
             
          
           
               
                   
                 7′b1?????? : Cycle_Offset &lt;= #FF_DELAY 12′h000; 
               
               
                   
                 7′b0?????0 : Cycle_Offset &lt;= #FF_DELAY Cycle_Offset; 
               
               
                   
                 7′b010???1 : Cycle_Offset &lt;= #FF_DELAY rx_cycletmrp[20:31]; //cycle synch write 
               
               
                   
                 7′b0?1???1 : Cycle_Offset &lt;= #FF DELAY Laint_wrdatap[20:31]; //cpu write has priority 
               
             
          
           
               
                   
                 7′b0001111 : Cycle_Offset &lt;= #FF_DELAY 12′h000; 
               
             
          
           
               
                   
                 7′b0000111 : Cycle_Offset &lt;= #FF_DELAY cycoff_incrmtrp[0:11]; 
               
               
                   
                 7′b000?0?1 : Cycle_Offset &lt;= #FF_DELAY Cycle_Offset; 
               
               
                   
                 7′b000?101 : Cycle_Offset &lt;= #FF_DELAY Cycle_Offset; 
               
               
                   
                 default : Cycle_Offset &lt;= #FF_DELAY 12′hxxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,load_cycsyncp,cpuwritep,cyc_offset_carry}) 
               
             
          
           
               
                   
                 end // always @ (posedge phy_sclkp) 
               
             
          
           
               
                   
                 // 
                 Generation of cyc_125usticp for updating Retry Timers etc. 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) begin 
               
             
          
           
               
                   
                 always _(posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 if(i_sresetp) cyc_set_cycpndp &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 eise if(˜i_resetp) cyc_set_cycpndp &lt;= #FF_DELAY cyctmrcntenp ? cyc_offset_carry: 
               
             
          
           
               
                   
                 catch_off_carryp; 
               
             
          
           
               
                   
                 else cyc_set_cycpndp &lt;= #FF_DELAY 1′bx; 
               
             
          
           
               
                   
                 end 
               
             
          
           
               
                 // 
                 assign cyc_set_cycpndp = cyc_125usticp; 
               
             
          
           
               
                 //bug81 cyc_125usticp should assert when we receive a cycle start pkt 
               
               
                 //and the cycle count is greater than ours (has just incremented) 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 if(i_sresetp) cyc_125usticp &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 else if(˜i_sresetp) cyc_125usticp &lt;= #FF_DELAY cyctmrcntenp? 
               
             
          
           
               
                   
                 (cyc_offset_carry | 
               
               
                   
                 load_cycsyncp &amp; 
               
               
                   
                 (Cycle_Count[0:12] != 
               
               
                   
                 rx_cycletmrp[7:19])): 
               
             
          
           
               
                   
                 catch_off_carryp; 
               
             
          
           
               
                   
                 else cyc_125usticp &lt;= #FF_DELAY 1′bx; 
               
             
          
           
               
                   
                 end 
               
             
          
           
               
                   
                 // 
                 clk8kinp synchronization and rise edge detection 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) begin 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 clk8kin_synclp &lt;= #FF_DELAY clk8kinp; 
               
               
                   
                 clk8kin_syncedp &lt;= #FF_DELAY clk8kin_synclp; 
               
               
                   
                 clk8kin_sync_dlyp &lt;= #FF_DELAY clk8kin_syncedp; 
               
               
                   
                 clk8kin_sync_dly2p &lt;= #FF_DELAY clk8kin_sync_dlyp; 
               
             
          
           
               
                   
                 end // always @ (posedge phy_sclkp) 
               
               
                   
                 assign clk8k_risep = clk8kin_syncedp &amp; ˜clk8kin_sync_dly2p; 
               
             
          
           
               
                   
                 // 
                 Carry from Cycle Count generation 
               
             
          
           
               
                   
                 assign cyc_count_carry = (Cycle_Count == ‘CYC_MOD_8000) &amp; cyc_offset_carry; 
               
               
                   
                 assign catch_cyccnt_carryp = ˜(catchup_cyccntp == ‘CYC_MOD_8000) &amp; 
               
             
          
           
               
                   
                 catch_off_carryp; 
               
             
          
           
               
                   
                 assign cyccnt_incrmtrp[0:12] = (cyctmrcntenp ? 
               
             
          
           
               
                   
                 catchup_cyccntp[0:12]: 
               
               
                   
                 Cycle_Count[0:12]) + 1′b1; 
               
             
          
           
               
                   
                 // 
                 Cycle Count Implementation 
               
             
          
           
               
                 /* 
                 always @ (posedge cyctmrclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,load_cycsyncp,cpuwritep,cyc_count_carry, 
               
             
          
           
               
                   
                 cyc_offset_carry))//synopsys parallel_case 
               
             
          
           
               
                   
                 5′b1???? : Cycle_Count &lt;= #FF_DELAY 13′h0000; 
               
               
                   
                 5′b010?? : Cycle_Count &lt;= #FF_DELAY rx_cycletmrp[7:19]; //cycle synch write 
               
               
                   
                 5′b0?1?? : Cycle_Count &lt;= #FF_DELAY i_aint_wrdatap[7:19]; //cpu write has priority 
               
               
                   
                 5′b0001? : Cycle_Count &lt;= #FF_DELAY 13′h0000; 
               
               
                   
                 5′b00000 : Cycle_Count &lt;= #FF_DELAY Cycle_Count; 
               
               
                   
                 5′b00001 : Cycle_Count &lt;= #FF_DELAY cyccnt_incrmtrp[0:12]; 
               
               
                   
                 default : Cycle_Count &lt;= #FF_DELAY 13′hxxxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,load_cycsyncp,cpuwritep,forwardp,cyc_count_carry}) 
               
             
          
           
               
                   
                 end // always @ (posedge cyctmrclkp) 
               
             
          
           
               
                 */ 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,load_cycsyncp,cpuwritep,cyc_count_carry, 
               
             
          
           
               
                   
                 cyc_offset_carry,llcreg_cyctmrenp})//synopsys parallel_case 
               
             
          
           
               
                   
                 6′b1????? : Cycle_Count &lt;= #FF_DELAY 13′h0000; 
               
             
          
           
               
                 //bug 2/11/1999   6′b1????0 : Cycle_Count &lt;= #FF_DELAY Cycle_Count 
               
             
          
           
               
                   
                 6′b0????0 : Cycle_Count &lt;= #FF_DELAY Cycle_Count; 
               
               
                   
                 6′b010??1 : Cycle_Count &lt;= #FF_DELAY rx_cycletmrp[7:19]; //cycle synch write 
               
               
                   
                 6′b0?1??1 : Cycle_Count &lt;= #FF_DELAY i_aint_wrdatap[7:19]; //cpu write has priority 
               
               
                   
                 6′b0001?1 : Cycle_Count &lt;= #FF_DELAY 13′h0000; 
               
               
                   
                 6′b000001 : Cycle_Count &lt;= #FF_DELAY Cycle_Count; 
               
               
                   
                 6′b000011 : Cycle_Count &lt;= #FF_DELAY cyccnt_incrmtrp[0:12]; 
               
               
                   
                 default : Cycle_Count &lt;= #FF_DELAY 13′hxxxx; 
               
             
          
           
               
                   
                 endcase // casez({_sresetp,load_cycsyncp,cpuwritep,forwardp,cyc_count_carry}) 
               
             
          
           
               
                   
                 end // always @ (posedge cyctmrclkp) 
               
               
                   
                 // 
               
             
          
           
               
                   
                 // 
                 Generation of cyc_set_cycsecp for CSU 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) begin 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 cyc_set_cycsecp &lt;= #FF_DELAY i_sresetp ? 1′b0: 
               
             
          
           
               
                 //bug51 
                 (cyctmrcntenp ? cyc_coun(_carry :catch_cyccnt_carryp;*/ 
               
             
          
           
               
                   
                 (cyc_count_carry | 
               
               
                   
                 (load_cycsyncp &amp; 
               
               
                   
                 Second_Count[0:6] != rx_cyctetmrp[0:6])); 
               
             
          
           
               
                   
                 end 
               
               
                   
                 assign seccnt_incrmtrp[0:6] = (˜cyctmrcntenp ? 
               
             
          
           
               
                   
                 catchup_seccntp[0:6]: 
               
               
                   
                 Second_Count[0:6]) + 1′b1; 
               
             
          
           
               
                 /* 
                 always @ (posedge catchupclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,rx_cyclesynchn,catch_cyccnt_carryp})//synopsys parallel_case 
               
             
          
           
               
                   
                 3′b1?? : catchup_seccntp[0:6] &lt;= #FF_DELAY 7′h00; 
               
               
                   
                 3′b00? : catchup_seccntp[0:6] &lt;= #FF_DELAY rx_cycletmrp[0:6]; 
               
               
                   
                 3′b010 : catchup_seccntp[0:6] &lt;= #FF_DELAY catchup_seccntp[0:6]; 
               
               
                   
                 3′b011 : catchup_seccntp[0:6] &lt;= #FF_DELAY seccnt_incrmtrp[0:6]; 
               
               
                   
                 default: catchup_seccntp[0:6] &lt;= #FF_DELAY 7′hxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,cpuwritep,rx_cyctesynchn,forwardp}) 
               
             
          
           
               
                   
                 end // always @ (posedge catchupclkp) 
               
             
          
           
               
                 */ 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,rx_cyclesynchn,catch_cyccnt_carry,llcreg_cyctmrenp})//synopsys parallel_case 
               
             
          
           
               
                   
                 4′b1???: catchup_seccntp[0:6] &lt;= #FF_DELAY 7′h00; 
               
               
                   
                 4′b0??0 : catchup_seccntp[0:6] &lt;= #FF_DELAY catchup_seccntp[0:6]; 
               
               
                   
                 4′b00?1 : catchup_seccntp[0:6] &lt;= #FF_DELAY rx_cycletmrp[0:6]; 
               
               
                   
                 4′b0101 : catchup_seccntp[0:6] &lt;= #FF_DELAY catchup_seccntp[0:6]; 
               
               
                   
                 4′b0111 : catchup_seccntp[0:6] &lt;= #FF_DELAY seccnt_incmrntrp[0:6]; 
               
               
                   
                 default : catchupseccntp[0:6] &lt;= #FF_DELAY 7′hxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,cpuwritep,rx_cyclesynchn,forwardp}) 
               
             
          
           
               
                   
                 end // always @ (posedge catchupclkp) 
               
             
          
           
               
                   
                 // 
                 Second Count Implementation 
               
             
          
           
               
                 /* 
                 always @ (posedge cyctmrclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,load_cycsyncp,cpuwritep,cyc_count_carry})//synopsys parallel_case 
               
             
          
           
               
                   
                 4′b1??? : Second_Count &lt;= #FF_DELAY 7′h00; 
               
               
                   
                 4′b010? : Second_Count &lt;= #FF_DELAY rx_cycletmrp[0:6]; //cycle synch write 
               
               
                   
                 4′b0?1? : Second_Count &lt;= #FF_DELAY i_aint_wrdatap[0:6]; //cpu write has priority 
               
               
                   
                 4′b0000 : Second_Count &lt;= #FF_DELAY Second_Count 
               
               
                   
                 4′b0001 : Second_Count &lt;= #FF_DELAY seccnt_incrmtrp[0:6]; 
               
               
                   
                 default: Second_Count &lt;= #FF_DELAY 7′hxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,load_cycsyncp,cpuwritep,forwardp,cyc_count_carry}) 
               
             
          
           
               
                   
                 end // always @ (posedge cyctmrclkp) 
               
             
          
           
               
                 */ 
               
             
          
           
               
                   
                 always @ (posedge phy_sctkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,load_cycsyncp,cpuwritep,cyc_count_carry,llcreg_cyctmrenp})//synopsys parallel_case 
               
             
          
           
               
                   
                 5′1???? : Second_Count &lt;= #FF_DELAY 7′h00; 
               
               
                   
                 5′b0???0 : Second_Count &lt;= #FF_DELAY Second_Count 
               
               
                   
                 5′b010?1 : Second_Count &lt;= #FF_DELAY rx_cycletmrp[0:6]; //cycle synch write 
               
               
                   
                 5′b0?1?1 : Second_Count &lt;= #FF_DELAY Laint_wrdatap[0:6]; //cpu write has priority 
               
               
                   
                 5′b00001 : Second_Count &lt;= #FF_DELAY Second_Count 
               
               
                   
                 5′b00011 : Second_Count &lt;= #FF_DELAY seccnt_incrmtrp[0:6]; 
               
               
                   
                 default: Second_Count &lt;= #FF_DELAY 7′hxx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,load_cycsyncp,cpuwritep,forwardp,cyc_count_carry}) 
               
             
          
           
               
                   
                 end // always @ (posedge cyctmrclkp) 
               
             
          
           
               
                   
                 // 
                 Generation of Cycle Request Signal to Transmitter for generating 
               
               
                   
                 // 
                 Cycle Start Packet 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) begin 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,tx_cycstrtdnn,llcreg_cmstrp,llcreg_cyctmrenp, 
               
             
          
           
               
                   
                 cyc_offset_carry}) //synopsys parallel_case 
               
             
          
           
               
                   
                 5′b1???? :cyc_reqn &lt;= #FF_DELAY 1′b1; 
               
               
                   
                 5′b00??? : cyc_reqn &lt;= #FF_DELAY 1′b1; 
               
               
                   
                 5′b01111 : cyc_reqn &lt;− #FF_DELAY 1′b0; 
               
               
                   
                 5′b010?? : cyc_reqn &lt;= #FF_DELAY cyc_reqn; 
               
               
                   
                 5′b01?0? : cyc_reqn &lt;= #FF_DELAY cyc_reqn; 
               
               
                   
                 5′b01??0 : cyc_reqn &lt;= #FF_DELAY cyc_reqn; 
               
               
                   
                 default : cyc_reqn &lt;= #FF_DELAY 1′bx; 
               
             
          
           
               
                   
                 endcase // casez({i_resetp,tx_cycstrtdnn,llcreg_cmstrp,llcrge_cyctmrenp, . . . 
               
             
          
           
               
                   
                 end // always @ (posedge phy_sclkp) 
               
             
          
           
               
                   
                 // 
                 Generation of Cycle Lost Signal is valid only for cycle slaves 
               
             
          
           
               
                 // 
                 always @ (posedge cycmon_sclkp) begin 
               
             
          
           
               
                   
                 always @ (posedge phy_sclkp) begin 
               
             
          
           
               
                   
                 casez({i_sresetp,cyc_set_cyclostp,exp_cycle_synch, 
               
             
          
           
               
                   
                 cyc_set_cycpnd/*cyc_*//*cyc_offset_carry*/})//synopsys parallel_case 
               
             
          
           
               
                   
                 4′b1??? : cyc_set_cyclostp &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 4′b01?? : cyc_set_cyctostp &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 4′b0011 : cyc_set_cyclostp &lt;= #FF_DELAY 1′b1; 
               
               
                   
                 4′b000? : cyc_set_cyclostp &lt;= #FF_DELAY cyc_set_cyclostp; 
               
               
                   
                 4′b00?0 : cyc_set_cyclostp &lt;= #FF_DELAY cyc_set_cyclostp; 
               
               
                   
                 default: cyc_set_cyclostp &lt;= #FF_DELAY 1′bx; 
               
             
          
           
               
                   
                 endcase // casez({i_sresetp,cyc_set_cyclostp,exp_cycle_synch,cyc_offset_carry}) 
               
             
          
           
               
                   
                 end // always @ (posedge phy_sclkp) 
               
             
          
           
               
                 // 
                 Generation of Expected Cycle Synch 
               
             
          
           
               
                   
                 always _(posedge phy_clkp) 
               
               
                   
                 begin 
               
             
          
           
               
                   
                 casez({i_sresetp, rx_cyclesynchn, cyc_set_cycpndp, 
               
             
          
           
               
                   
                 cyc_set_cyclostp} | 4′h0) 
               
             
          
           
               
                   
                 4′b1??? : exp_cycle_synch &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 4′b00?? : exp_cycle_synch &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 4′b0110 : exp_cycle_synch &lt;= #FF_DELAY 1′b1; 
               
               
                   
                 4b0100 : exp_cycle_synch &lt;= #FF_DELAY exp_cycle_synch; 
               
               
                   
                 4′b01?1 : exp_cycle_synch &lt;= #FF_DELAY 1′b0; 
               
               
                   
                 default : exp_cycle_synch &lt;= #FF_DELAY 1′bx; 
               
             
          
           
               
                   
                 endcase 
               
             
          
           
               
                   
                 end 
               
             
          
           
               
                 endmodule