Patent Document

BACKGROUND  
       [0001]     Logic analyzers in use today function by observing multiple channels&#39; incoming digital data and performing a data storage function based upon bit patterns identified in the incoming data. The intelligence of the logic analyzer lies in its sequencer, which observes the incoming data signals, and produces signaling based upon the incoming data patterns. The signaling is typically a set of output signals that direct other areas of the logic analyzer to perform functions. A user is able to designate those functions performed and what input patterns cause the designated functions to be performed. The sequencer of the logic analyzer is a programmable state machine that makes decisions based upon patterns in the incoming data. One method of implementing a state machine is to provide a look up table (herein “LUT”). As such, the LUT accepts a current state of the sequencer and the incoming data as inputs that provides output indicating a new state of the sequencer and signaling destined to initiate performance of designated functions. Ideally, the sequencer operates at the speed of the incoming data. As data speeds and number of channels increase, however, it becomes more difficult to provide a sequencer fast enough to accommodate the incoming data.  
         [0002]     One method for addressing the data speed challenge is to de-multiplex the incoming data to a more manageable speed for the LUT. For each de-multiplex factor, however, memory requirements to implement the sequencer increase geometrically and the solution quickly becomes prohibitively costly. Additionally, it takes more time to process de-multiplexed data through the sequencer and at some point, the benefits gained through de-multiplexing are lost due to increased processing time. Another method is to cascade the LUTs to reduce the memory requirements. Disadvantageously, however, each LUT and interconnecting logic must still operate at the speed of the incoming data. Incoming digital data speeds are currently at 2 GHz and increasing. Using current technology, cascaded LUTs are not able to operate at that speed.  
         [0003]     There is a need, therefore, to provide a sequencer that can operate at speed for incoming digital data with an opportunity for improved speeds as technology progresses. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]     An understanding of the present teachings can be gained from the following detailed description, taken in conjunction with the accompanying drawings of which:  
         [0005]      FIG. 1  is a block diagram of a logic analyzer.  
         [0006]      FIG. 2  is a circuit diagram of a sequencer according to the present teachings.  
         [0007]      FIG. 3  is a circuit diagram of sequencing element according to the present teachings.  
         [0008]      FIG. 4  is a flow chart of a process according to the present teachings.  
         [0009]      FIGS. 5 and 6  illustrate another embodiment of a sequencer and sequencing element respectively according to the present teachings.  
         [0010]      FIGS. 7, 8 , and  9  illustrate another embodiment of a sequencer and sequencing element according to the present teachings.  
     
    
     DETAILED DESCRIPTION  
       [0011]     With specific reference to  FIG. 1  there is shown basic building blocks of a logic analyzer including sequencer  102  according to the teachings of the present invention. The logic analyzer accepts incoming digital data  106  from DUT  108 , which is latched into state capture register  104  by DUT clock  110 . De-multiplexer  122  accepts capture register output  107  and de-multiplexes it  8  to  1  for simultaneous presentation of the de-multiplexed data  126  to resource generator  123  and latency matching register  112 . The resource generator  123  accepts the de-multiplexed data  126  and compares it against patterns  125  established by a user. Results of the pattern matches within the resource generator  123  generate resources  124 . Because the resources  124  are de-multiplexed, further data processing is able to proceed at a slower speed than the incoming data rate. The sequencer  102  accepts the resources  124 , and generates one or more control signals  114 ,  116  for data storage. The control signals  114 ,  116  from the sequencer  102 , referred to as trigger  114  and store  116 , are connected to trace formatter  118 . The trace formatter  118  accepts an output  128  of the latency matching register  112  and selectively stores one or more cycles of the incoming digital data patterns  130  in memory  120  for eventual presentation to a logic analyzer user. In a specific embodiment, the trigger control signal  114  anchors the logic analyzer measurement in time. The store control signal  116  controls whether any one cycle of digital data is stored in the memory  120 .  
         [0012]     With specific reference to  FIG. 2  of the drawings, there is shown a first embodiment of a sequencer  102  according to the present teachings comprising a plurality of sequencing elements  200 . In a specific embodiment, the de-multiplexer  122  de-multiplexes the output of the state capture register  104  8 to 1. Other embodiments may have a different de-multiplexing multiple. Because of the 8 to 1 multiplexing in the specific embodiment, there is one resource cycle for every 8 cycles of incoming data  106 . In the specific embodiment that uses the 8 to 1 de-multiplexing, there are eight sequencing elements  200 , one sequencing element that processes each data cycle. The sequencing elements  200  are connected in a cascaded combination interconnected by actual next state  218  and actual previous state  219  signals. The actual next state output  218  from a first one of the sequencing elements  200   a  becomes the actual previous state input  219  of a second one of the sequencing elements  200   b . All sequencing elements  200  are similarly interconnected. The actual next state  218  of the 8 th  sequencing element  200   h  is latched into state latch  302 . An output of the state latch  304  is connected to the actual previous state input  219  of the 1 st  sequencing element  200   a . Accordingly, the actual next state  218  of a last one of the sequencing elements  200   h  informs the first one of the sequencing elements  200   a  in a next resource cycle. The sequencing elements  200 , therefore, have 8 cycles of the incoming data to properly process a current resource cycle before receiving a next resource cycle. Each sequencing element  200  generates the store and trigger control signals  114 ,  116  for presentation to the trace formatter  118 . The data path through the latency matching register  112  and trace formatter  118  is similarly de-multiplexed and proceeds in parallel with processing that proceeds in the sequencer  102 . From a timing perspective, the control signals  114 ,  116  from the first sequencing element  200   b  relate to control of the first cycle of every 8 cycles of the incoming data  106 , control signals  114 ,  116  from the second sequencing element  200   b  relate to control of the second cycle of every 8 cycles of the incoming data  106 , and the control signals  114 ,  116  from the eighth sequencing element  200   h  relate to control of the last cycle of every 8 cycles of the incoming data  106 . In a specific embodiment, therefore, there are 8 store control signals  114  and 8 trigger control signals  116  that are received by the trace formatter  118 .  
         [0013]     With specific reference to  FIG. 3  of the drawings, there is shown an embodiment of the first sequencing element  200   a  according to the present teachings in which there are four memories that function as respective first, second, third and fourth look up tables  201 - 204 , respectively. Each look up table  201 - 204  is configured to determine a next possible state  205 - 208  for each one of four possible previous states based upon its inputs  124   a . The first look up table  201  determines the next possible state  205  based upon the inputs  124   a  assuming the previous actual state is state 0 , the second look up table  202  determines the next possible state  206  based upon the same inputs  124   a  assuming the previous actual state is state 1 , the third look up table  203  determines the next possible state  207  based upon the same inputs  124   a  assuming the previous actual state is state 2 , and the fourth look up table  204  determines the next possible state  208  based upon the same inputs  124   a  assuming the previous actual state is state 3 . The illustrative example discusses a 4-state state machine. Alternative embodiments of the sequencing element for a state machine with more than four states may have additional look up tables to accommodate the additional states. Each look up table  201 - 204  accepts as its input  124   a , a subset of the resources  124 . As the resources subset  124   a  is presented to the look up tables  201 - 204 , the respective possible next states  205 - 208  are presented at the output of the look up tables  201 - 204 . Because the sequencer of the present teachings is a state machine, an actual next state is based upon the incoming data  106  as well as an actual previous state. The multiple next state determinations provide a conditional next state for all previous state possibilities and at the look up table processing stage, are independent of the actual previous state  219 . The possible next states  205 - 208  are latched into first, second, third, and fourth sequencer registers  209 - 212 . The sequencing element clocking signal  220  for the first through fourth sequencing registers  209 - 212  comprises a derivative of the DUT clock  110 . In the embodiment with 8 to 1 de-multiplexing, the clocking signal  220  is synchronized with and is ⅛ th  the frequency of the DUT clock  110 . An output  213 - 216  of each sequencer register  209 - 212  reflects each one of the next possible states  205 - 208  and is presented to sequencer multiplexer  217 . The sequencer multiplexer  217 , with all possible next states available to it, selects an actual next state  218  among the next possible states  205 - 208  based upon an actual previous state  219 . Advantageously, determination of the possible next states  205 - 208  is able to occur before or in parallel with the determination of the actual previous state  219 . Final determination of the actual next state  218 , therefore, is a matter of multiplexer selection, which is a faster process than the look up table operation. The output of the look up tables  205 - 208  also include values for the trigger  114  and store  116  control signals relative to the subset of resources  124   a  being processed. Each sequencing element  200  in  FIG. 2  has the structure of the sequencing element shown in  FIG. 3 . As the actual next state  218  from the first resource subset  124   a  is determined by the first sequencing element  200   a , it is presented as the actual previous state to the second sequencing element  200   b . The sequencer multiplexer  217  of the second sequencing element  200   b  then is able to make its selection of the actual next state  218  from the second resource subset  124   b  and presents it to the third sequencing element  200   c . Accordingly, the actual next states  218  ripple through the sequencing elements  200   a  through  200   h . Because all possible next states are already available to the sequencer multiplexers  217 , determination of the actual next states  218  are able to ripple through very rapidly. As the 8 th  sequencing element  200   h  makes its determination, all resources  124  of the present resource cycle are processed. The actual next state  219  of the 8 th  sequencing element  200   h  from a last resource cycle is then stored into the state latch  302 . The actual previous state  219  for a next sequencing cycle, therefore, is maintained at the state latch output  304  in preparation for the next resource cycle. As one of ordinary skill in the art appreciates from a review of  FIGS. 2 and 3 , the look up table processing for each resource subset  124   a  through  124   h  occurs in parallel and provides each of the sequencer multiplexers  217  with all possible next states at the respective inputs  213  through  216 .  
         [0014]     With specific reference to  FIG. 4  of the drawings, there is shown a flow chart of the process according to the present teachings. In a specific example of a logic analyzer that uses a sequencer according to the present teachings, there are N bits of incoming data  106  from the DUT  108  and the DUT clock  110  and six user specified pattern matches. The resource generator  123  compares each of the 8 de-multiplexed data states against the 6 patterns matches to generate 6 compare results bits per data cycle. For 8 to 1 de-multiplexing  402 , the resource generator  122 , therefore, generates 6×8=48 bits of resource  124  for presentation to the sequencer  102 . Each of eight sequencing elements  200  receives a 6-bit resource subset  124   a  through  124   h , respectively. The resource subsets  124   a  through  124   h  are presented  404  simultaneously to the respective sequencing elements  200   a  through  200   h . The look up tables  201  through  204  in each sequencing element  200   a  through  200   h  determine  406  all possible next states  205  through  208  for each respective resource subset  124   a  through  124   h . Each possible next state  205  through  208  are latched into sequencing registers  209 - 212  in each sequencing element  200   a  through  200   h  and are thereby made available at the input of the sequencer multiplexer  217 . As the actual previous state  219  is made available from a previous sequencing element, the sequencer multiplexer  217  selects  408  one of the possible next states available at its input as the actual next state  218 . As each actual next state  218  from a previous sequencing element  200  is communicated  410  to the next sequencing element  200 , the sequencing multiplexers  217  make the appropriate actual next state selection and ripples the actual next state  218  as the actual previous state  219  through the sequencer  102 . The actual next state  218  of the 8 th  sequencing element  200   h  is latched into state latch  302  and is presented as the actual previous state  219  to the 1 st  sequencing element  200   a  for use in the next resource cycle. The process of determining all possible next states, selecting an actual next state and communicating the actual next state  218  as the actual previous state  219  to the next sequencing element  200  repeats  412 .  
         [0015]     As part of the sequencer processing, a logic analyzer counter starts at some programmable value and may be decremented by any sequencing element  200   a  through  200   h  based upon a value of the resource subsets  124   a  through  124   h . As an example, a logic analyzer may be programmed to trigger after some number of matches to a particular pattern or range. To perform such a function, the counter is loaded with a value and the value is decremented for each match until the counter reaches a terminal count at which time it performs the programmed function. When the counter reaches the terminal count, the sequencer  102  performs the action according to one programmed for the terminal count condition. To implement the counter in a sequencer embodiment according to the present teachings, each sequencing element  200  processes the counter for each respective resource subset. A logic analyzer counter is desirably of a significant width. The wider the counter, however, the more time required for counter processing. In a specific embodiment, the counter is a 24-bit element. In order to reduce the amount of circuitry and processing time to process the counter, the 24-bit counter is reduced to a 4-bit counter proxy that is used within each one of the sequencing elements  200 . The counter proxy is established by reduction OR&#39;ing the highest 21 bits of the counter as the 4 th  bit, with the lowest 3 bits of the counter used as is. Because the sequencer  102  in a specific embodiment operates on 8 cycles of data within a single resource cycle, the 4-bit counter proxy is sufficient information to determine if the counter reaches terminal count within the 8 data cycles and to process through all sequencing elements  200  without losing counter coherency.  
         [0016]     With specific reference to  FIG. 5  of the drawings, there is shown another embodiment of the sequencer  102  that includes circuitry for processing the counter and counter proxy. The counter proxy is processed by each sequencing element  200   a  through  200   h  as a straightforward 4-bit counter. After all eight sequencing elements  200  have processed the resources  124  and the counter proxy, counter clean-up circuitry  550  restores the coherency of the full 24-bit counter in preparation for processing the next resource cycle. During resource processing, there are certain conditions that cause the counter to be reset by the sequencing elements  200 . As an example, the counter may be counting pattern or range matches in the data, but also is programmed to be reset if another pattern is found. In the event of a reset, the counter is loaded with a reset value. In a specific logic analyzer implementation, there are first, second, third and fourth 24-bit counter reset values  510 ,  511 ,  512 , and  513 , received by each sequencing element  200 . In the event of a reset condition, the sequencing element  200  selects one of the counter reset values  510  through  513  depending upon a current state of the sequencer  102 . A 4-bit previous counter proxy  501  is received by each sequencing element, for example  200   b , from a previous sequencing element, for example  200   a . Each sequencing element  200  calculates the next counter proxy  503  based upon the respective resource subset  124  and the previous counter proxy value  501 . The next counter proxy  503  is presented as the previous counter proxy  501  to the next sequencing element  200 . A counter register  505  stores the current counter value for presentation to the 1 st  sequencing element  200   a  in the next resource cycle. Because the sequencing elements  200  process the counter proxy, there is counter clean-up circuitry disposed at the output of the 8 th  sequencing element  200  for restoring the coherency of the 24-bit value maintained in the counter register  505 . Accordingly, the counter register  505  maintains the correct counter value for each resource cycle.  
         [0017]     A reset of the sequencer  102  based upon the resources  124  causes the counter to be reset. The counter may be reset to a different reset value depending upon a current state of the sequencer  102 . Accordingly, in a 4-state sequencer, there are four respective counter reset values  510  through  513 . A 1-bit reset and a 2-bit reset state are rippled through the eight sequencing elements  200  to maintain the reset information over the resource cycle for the counter clean-up circuitry  550 . The beginning of the resource cycle has no reset, so logic “0”s are established as a first reset in  514   a  and reset state in  515   a . As the signals are rippled through each sequencing element  200 , each sequencing element  200  accepts the reset in  514  and reset state in  515  signals from the previous sequencing element  200 . If no reset occurs within the sequencing element  200 , the reset in  514  and state reset in  515  are passed through to the next sequencing element  200  unchanged as reset out  516  and state reset out  517 . During a current resource cycle, a previous counter value  501  is decremented or not depending upon the resources  124   a  and is passed to the next sequencing element  200  as a next counter value  503 , which is received by the next sequencing element  200  as the previous counter value  501 . If a reset occurs as a result of the respective resource subset  124   a  through  124   h , the sequencing element  200  sets the reset out  516  for presentation as the reset in  514  to the next sequencing element  200  indicating that a reset has occurred within the current resource cycle. In the event of a reset, the sequencing element  200  also sets the reset state out  517  indicating the state in which the reset occurred. The reset state out  517  is presented to the next sequencing element  200  as the reset state in  515 . The sequencing element  200  further resets the counter proxy out  503  to an appropriate counter proxy reset value based upon one of the counter reset values  510  through  513  as determined by the sequencing element next state. After the reset state  517  and reset signals  514  are processed by all sequencing elements  200 , the counter clean-up circuitry  550  restores the coherency of the counter value for the next resource cycle. Because the sequencing elements  200  treat the 4 bit counter proxy as a straightforward counter, the highest bit of the 4-bit counter proxy out  503  from the last sequencing element  200   h  is an indication of whether a borrow has occurred within the last resource cycle against the highest 21 bits of the counter for which the highest 4 th  bit is a proxy. Specifically, a borrow on the highest bit of the 4 bit count proxy has occurred when the 4 th  bit of the count proxy out  503  of the last sequencing element is a “0”). A zero value for the 4 th  bit of the count proxy out  503  for the last sequencing element, therefore, indicates a decrement of the highest 21 bits of the counter in preparation for the next resource cycle. If no borrow is made on the highest bit of the 4 bit counter proxy out  503 , i.e. when the value of the 4 th  bit of the count proxy out is a “1”, no decrement is indicated for the highest 21 bits of the counter. The counter clean up circuitry calculates the correct value of the upper 21 bits of the counter in the event of a reset by accepting the upper 21 bits of each counter reset value  510 - 513 , decrementing  549  each value by one, and presenting the decremented values to a 4:1 first state counter multiplexer  551 . The same upper 21 bits of each counter reset value are also presented un-decremented to 4:1 second state counter multiplexer  552 . Selection of which of the four possible inputs into the decrement reset counter multiplexer  551  and the reset counter multiplexer  552  is made using the state reset out  517 . Therefore, there are two possible upper 21 bits of the counter available at the output of the first and second state counter multiplexers  551 ,  552  representing the upper 21 bits of the counter if there were a reset and a borrow indicated by the proxy and if there were a reset but no borrow indicated by the proxy. Also pre-calculated in the counter clean up circuitry are the decremented and un-decremented values of the current counter. The decremented and un-decremented values of the current counter are presented as inputs to respective first and second reset multiplexers  553 ,  554 . The other input to the first and second reset multiplexers  553 ,  554  is the output of the respective first and second state counter multiplexers  551 ,  552 . Selection of which value is presented at the output of the first and second reset multiplexers  553 ,  554  is made based on the reset out  514  of the last sequencing element  200   h . Accordingly, the outputs of the first and second reset multiplexers provide the correct upper 21 bits of the counter for the decremented and undecremented conditions having already processed any reset condition. The outputs of the first and second reset multiplexers  553 ,  554  are presented to borrow selection multiplexer  555 . A proxy bit  556  of the counter proxy out  503  from the last sequencing element  200   h  provides selection of which of the inputs presented to the borrow selection multiplexer  555  is presented at its output. If the proxy bit  556  has a 0 value, a borrow has occurred at some point in the last resource cycle and the decremented selection of the correct upper 21 bits of the counter is made. If the proxy bit  556  has a 1 value, a borrow has not occurred and the undecremented selection of the correct upper 21 bits of the counter is made. The output of the borrow selection multiplexer  555 , therefore, represents the correct upper 21 bits of the counter after reset and borrow processing. The output of the borrow selection multiplexer  555  is recombined with the lowest 3 bits of the count out  503  for storage in the counter register  505 , which is latched at the next clock edge. Accordingly, a value in the counter register  505  reflects the correct counter value. The lowest 3 bits of the counter register  505  are then fed back as the lowest 3 bits of the previous counter proxy value  501  for the first sequencing element  200   a  in the next resource cycle. The upper 21 bits of the counter register  505  are reduction OR&#39;d as the counter proxy bit of the previous counter proxy value  501  for the first sequencing element  200   a  in the next resource cycle. The upper 21 bits are also presented to the clean up circuitry  550  for use in counter processing in the next resource cycle.  
         [0018]     With specific reference to  FIG. 6  of the drawings, there is shown an embodiment of a sequencing element  200  according to the present teachings. The embodiment of  FIG. 6  is configured to implement the same 4-state state machine as shown in  FIG. 3  of the drawings, but also to handle counter processing as discussed with respect to  FIG. 5 . In the embodiment of  FIG. 6 , there are first and second sets of the four look up tables in each sequencing element  200 . A first set of look up tables  201   a  through  204   a  determine four possible next states  213   a  through  216   a  based upon the resources subset  124   a  when a terminal count condition is false. The second set of four look up tables  201   b  through  204   b  determine the four possible next states  213   b  through  216   b  based upon the resources subset  124   a  when a terminal count condition is true. Each set of look up tables  201   a  through  204   a  and  201   b  through  204   b  has respective sequencer multiplexers  217   a  and  217   b  associated with it. Each sequencer multiplexer  217   a ,  217   b  receives the actual previous state  219  to control selection of each sequencer multiplexer output. The embodiment of  FIG. 6  also has a counter look up table  622  that accepts the same resource subset  124   a  as presented to the look up tables  201   a  through  204   a  and  201   b  through  204   b . The counter look up table  622  determines four possible 1-bit decrement signals  623  indicating whether the counter is to be decremented or not based upon the resources subset  124   a  for each possible state. The four possible decrement signals  623  are stored into 4-bit decrement latch  624 . Counter multiplexer  626  accepts the four possible decrement signals  623  and makes selection of the actual decrement signal  628  based upon the actual previous state  219 . The previous counter proxy  501  is received by the sequencing element  200  from the previous sequencing element  200 . The previous counter proxy  501  is checked against a value of 1 at counter compare  636 . If the previous counter proxy  501  is equal to 1, the counter compare  636  presents a 1 at a counter compare output  638 . If the previous counter proxy value is equal to anything except 1, the counter compare  636  presents a “0” at its output  638 . The counter compare output  638  and actual decrement control signal  628  are inputs into 2-input AND terminal count gate  643 . An output of the terminal count gate  640  provides a terminal count status  645  that indicates whether the counter is at its terminal count. If so, terminal count multiplexer  642  selects the output of sequencer multiplexer  217   b  related to a terminal count status of true. If not, the terminal count multiplexer  642  selects the output of sequencer multiplexer  217   a  related to a terminal count status of false.  
         [0019]     As part of the counter processing in the sequencing element  200 , the sequencing element  200  accepts the lowest 3 bits of each counter reset value  510  through  513  including a reduction OR&#39;d result of the upper 21 bits as first through fourth counter reset proxies  610 - 613 . Each look up table  210  through  204  has associated with it, a respective counter reset proxy multiplexer  614   a  through  617   a  and  614   b  through  617   b . Selection of an appropriate possible counter reset proxy  619  for each possible state is made by a next state output  618  of each look up table  201   a  through  204   a  and  201   b  through  204   b . The possible counter reset proxy value  619  is combined with the output of the respective look up table  201   a  through  204   a  and  201   b  through  204   b , which includes 2 bits of next state information, store, trigger, and reset, for a total of 9 bits of information. Selection of an appropriate counter reset proxy for the terminal count false  619   a  and terminal count true  619   b  conditions is, therefore, made by the sequencing multiplexers  217   a ,  217   b  as part of the actual next state  218 , store  114 , trigger  116  and reset determination. The two possible counter reset proxies  619   a ,  619   b  as well as the two possible next states as calculated by the look up tables  201   a - 204   a  and  201   b - 204   b  are presented to first and second proxy/reset multiplexers  620 ,  621 . The other input to the first and second proxy/reset multiplexers  620 ,  621  is the actual counter proxy  503 . The actual counter proxy  503  is processed by the sequencing element  200  by accepting previous counter proxy value  501 , decrementing it by one at reference numeral  632  and then presenting the decremented value to decrement multiplexer  634 . The un-decremented counter proxy  501  is also presented to the decrement multiplexer  634 . Selection between the decremented counter proxy value from  632  versus the un-decremented counter proxy value is made with actual decrement signal  628 . As described above, selection between the decremented/un-decremented counter proxy and the counter reset proxy  619   a ,  619   b  for the terminal count conditions of true and false is made by current reset  640   a ,  640   b  at first and second proxy/reset multiplexers  620 ,  621 . The outputs of the first and second proxy/reset multiplexers  620 ,  621  provide the two possible counter proxies, store, trigger, next state, reset for the terminal count conditions of true and false. The two possible grouping are selected using the terminal count multiplexer  642  to determine the actual counter proxy  503 , store  114 , trigger  116 , actual next state  218  and current reset  644 . The current reset  644  is conjunctively combined at reset AND gate  650  before presentation as the reset out  516 .  
         [0020]     With specific reference to  FIG. 7  of the drawings, there is shown another embodiment of a sequencer  102  according to the present teachings wherein a determination of the store and trigger  114 ,  116  is removed from the next state, count and reset determinations and placed in a parallel functional block. In the embodiment of  FIG. 7 , there are primary and secondary sequencing elements  200 ,  700  that communicate across sequencing element interface  702 . In an embodiment that uses 8:1 data to resource de-multiplexing, there are eight of the primary sequencing elements  200   a  through  200   h  communicating with eight of the secondary sequencing elements  700   a  through  700   h  over respective sequencing element interfaces  702   a  through  702   h . Each sequencing element interface  702  comprises a state on  719 , which is a latched value of the actual previous state  219 , a store array  703  comprising the store signal for each possible next state for the terminal count true condition and the store signal for each possible state for the terminal count false condition, a trigger array  704  for each possible next state for the terminal count true condition and the trigger signal for each possible state for the terminal count false condition, and the terminal count status  645 . The store and trigger arrays  703 ,  704  are 8-bits each. The secondary sequencing element  700   a  accepts the state on  719 , the store and trigger arrays  703 ,  704  and terminal count  645  and determines the store  114  and trigger for each sequencing element  200 / 700 . The inputs into each sequencing element and the counter clean-up circuitry are the same as shown and described in  FIGS. 5 and 6 .  
         [0021]     With specific reference to  FIG. 8  of the drawings, there is shown an embodiment of the primary sequencing element  200  according to the present teachings wherein an adaptation is made from the sequencing element of  FIG. 6  by bringing out a possible store and trigger  703 ,  704  from each look up table output and latching it into a store/trigger memory element  705 . Each look up table is related to a respective one of the store/trigger memory elements  703 ,  704 . In a specific embodiment where there are two distinct sets of look up tables for true and false terminal count conditions, there are also possible store and trigger  703 ,  704  for both terminal count conditions. Accordingly, in the illustrated embodiment, look up table  201   a  is related to possible store bit  703   a  and possible trigger bit  704   a , look up table  202   a  is related to possible store bit  703   b  and possible trigger bit  704   b  and look up table  204   b  is related to possible store bit  703   h  and possible trigger bit  704   h.    
         [0022]     With specific reference to  FIG. 9  of the drawings, the secondary sequencing element  700  performs final determination of the store  114  and trigger  116  for each primary sequencing element/secondary sequencing element  200 / 700  combination. Each secondary sequencing element  700  accepts the store  703  and trigger  704  arrays over the sequencing element interface  702 . The possible store and trigger bits for a terminal count condition of false are presented to a first secondary sequencing element multiplexer  901 . Similarly, the possible store and trigger bits for a terminal count condition of true are presented to a second secondary sequencing element multiplexer  902 . Selection of an appropriate one of the possible store and trigger bits is made using the state on  719  signal for the terminal count false and true conditions. Determination of the final store  114  and trigger  116  is made by presentation of the appropriate store and trigger bits for the terminal count conditions of false and true to a tertiary secondary sequencing multiplexer  903  with selection made using the terminal count  645 . An output of the tertiary secondary sequencing multiplexer  903  is the store/trigger  114 ,  116  for the primary and secondary sequencing element  200 / 700  combination.  
         [0023]     Embodiments according to the present teachings are described herein by way of illustration. Other embodiments not specifically disclosed and within the scope of the appended claims will occur to one of ordinary skill with benefit of the present teachings. For example, as previously mentioned herein, the present teachings are applicable to many different de-multiplexing factors. De-multiplexing factors larger than 8 to 1 result in a larger circuit area to implement the circuit, however, they may produce better operating speeds. As the de-multiplexing factors increase, the circuit eventually suffers from too many layout parasitic impedances and operating speeds deteriorate. It is found that the 8 to 1 de-multiplexing is currently preferred in view of current technology. In another example of an alternate embodiment, the previous and next states may be represented with 4-bit one hot encoding as opposed to the disclosed 2-bit binary encoding. The 4-bit one hot encoding may result in an incremental increase in speed because the binary input multiplexers  217  that process the previous state information may be replaced with logic in each of the sequencing elements  200 .

Technology Category: 3