Abstract:
An apparatus and method for detecting concatenation of payload data for an communication circuit is disclosed, wherein the payload data is dispersed over a first integrated circuit and one or more subsequent integrated circuits. The method and apparatus include determining whether each of the one or more subsequent integrated circuits have all channels therein designated as concatenation slaves, and communicating the determination to the first integrated circuit, the determination indicating that the one or more subsequent integrated circuits. According to an embodiment, the method and apparatus further include coupling the first integrated circuits to the one or more subsequent integrated circuits. The apparatus and method further include detecting concatenation on a first integrated circuit of the one or more integrated circuits, assigning one or more bi-directional ports coupled to the first integrated circuit as an input port, assigning each bi-directional port coupled to the one or more subsequent integrated circuits as output ports, and if any one integrated circuit among the subsequent integrated circuits includes a channel therein designated as a slave channel, providing an active high signal to the output port, the active high signal coupled to the input port of the first integrated circuit.

Description:
This application claims the benefit of Provisional Application No. 60/211,830, filed Jun. 15, 2000. 
     CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is related to patent application Ser. No. 09/477,166, filed Jan. 4, 2000, and entitled “METHOD AND APPARATUS FOR A REARRANGEABLY NON-BLOCKING SWITCHING MATRIX,” having A. N. Saleh, D. E. Duschatko and L. B. Quibodeaux as inventors. This application is assigned to Cisco Technology, Inc., the assignee of the present invention, and is hereby incorporated by reference, in its entirety and for all purposes. 
     This application is related to patent application Ser. No. 09/232,395, filed Jan. 15, 1999, and entitled “A CONFIGURABLE NETWORK ROUTER,” having H. M. Zadikian, A. N. Saleh, J. C. Adler, Z. Baghdasarian, and V. Parsi as inventors. This application is assigned to Cisco Technology, Inc., the assignee of the present invention, and is hereby incorporated by reference, in its entirety and for all purposes. 
     This application is related to patent application Ser. No. 09/609,577 filed Jun. 30, 2000, and entitled “FIXED ALGORITHM FOR CONCATENATION WIRING,” having Robert A. Hall, and V. Parsi as inventors. This application is assigned to Cisco Technology, Inc., the assignee of the present invention, and is hereby incorporated by reference, in its entirety and for all purposes. 
     This application is related to patent application Ser. No. 09/607,912 filed Jun. 30, 2000, and entitled “PATH AIS INSERTION FOR CONCATENATED PAYLOADS ACROSS MULTIPLE CHIPS,” having Douglas E. Duschatko, Lane Byron Quibodeaux, Robert A. Hall, Andrew J. Thurston as inventors. This application is assigned to Cisco Technology, Inc., the assignee of the present invention, and is hereby incorporated by reference, in its entirety and for all purposes. 
     This application is related to patent application Ser. No. 09/608,461 filed Jun. 30, 2000, and entitled “CHANNEL ORDERING FOR COMMUNICATION SIGNALS SPLIT FOR MATRIX SWITCHING,” having Douglas E. Duschatko, Lane Byron Quibodeaux, Robert A. Hall, Andrew J. Thurston as inventors. This application is assigned to Cisco Technology, Inc., the assignee of the present invention, and is hereby incorporated by reference, in its entirety and for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to data communications, and, more particularly, efficiency in data communication circuits. 
     2. Description of the Related Art 
     A data communications network is the interconnection of two or more communicating entities (i.e., data sources and/or sinks) over one or more data links. A data communications network allows communication between multiple communicating entities over one or more data communications links. High bandwidth applications supported by these networks include streaming video, streaming audio, and large aggregations of voice traffic. In the future, these demands are certain to increase. To meet such demands, an increasingly popular alternative is the use of lightwave communications carried over fiber optic cables. The use of lightwave communications provides several benefits, including high bandwidth, ease of installation, and capacity for future growth. 
     The synchronous optical network (SONET) protocol is among those protocols designed to employ an optical infrastructure and is widely employed in voice and data communications networks. SONET is a physical transmission vehicle capable of transmission speeds in the multi-gigabit range, and is defined by a set of electrical as well as optical standards. 
     In some networks, network nodes store data which they use for proper operation. In SONET, data between adjacent nodes are transmitted in modules called STS&#39;s (synchronous transport signals). Each STS is transmitted on a link at regular time intervals (for example, 125 microseconds). See Bellcore Generic Requirements document GR-253-CORE (Issue 2, December 1995) incorporated herein by reference. An STS-1 is a Synchronous Transport Signal-level 1 is the basic module in SONET and is defined as a specific sequence of 810 bytes (6480 bits) including overhead bytes and an envelope capacity for transporting payloads. In general, the higher-level signals, the STS-N signals, are lower-level modules that are multiplexed together and converted to an OC-N or STS-N signal. An STS-N frame is a sequence of N×810 bytes wherein N is a predetermined number. An STS-N is formed by byte-interleaving of STS-1 and STS-M modules, wherein M is less than N. 
     In some systems, such as certain ISDN and ATM systems, multiple STS-1 payloads are transported as super rate payloads. To accommodate such a payload an STS-Nc module is formed by linking N constituent STS-1s together in fixed phase alignment. The payload is then mapped into a single STS-Nc Synchronous Payload Envelope (SPE) for transport. Network equipment supporting the multiplexing, switching or transport of STS-Nc SPES treat an STS-Nc SPE as a single entity. When an STS-Nc SPE is treated as a single entity, concatenation indicators are present in the second through the Nth STS payload pointers which show that the STS-1s in the STS-Nc are linked together. The concatenation indicators do not, however, indicate when a concatenated STS-Nc is spread across multiple ASICs (Application Specific Integrated Circuit). Moreover, typically ASIC devices have limited pin availability compounding the problem. 
     It is desirable to have a system and method for detecting a concatenated STS-Nc that is spread across multiple ASICs. 
     SUMMARY OF THE INVENTION 
     Accordingly a system and method for detecting concatenation of payload data in a communication circuit, wherein the payload data is dispersed over a first integrated circuit and one or more subsequent integrated circuits, includes determining whether each of the one or more subsequent integrated circuits have all channels therein designated as concatenation slaves, and communicating the determination to the first integrated circuit, the determination indicating that the one or more subsequent integrated circuits are concatenation slaves. According to an embodiment, the method includes coupling the first integrated circuits to the one or more subsequent integrated circuits. The method further includes detecting concatenation on a first integrated circuit of the one or more integrated circuits, assigning one or more bi-directional ports coupled to the first integrated circuit as an input port, assigning each bi-directional port coupled to the one or more subsequent integrated circuits as an output port, and if any one integrated circuit among the subsequent integrated circuits includes a channel therein designated as a slave channel, providing an active high signal to the output port, the active high signal coupled to the input port of the first integrated circuit. 
     In one embodiment, the concatenation detection includes coupling the integrated circuits with a wire. The wire is further coupled to a pull up resistor to enable an active low signal and a tri stated signal. In another embodiment, the integrated circuits are disposed on an ASIC. 
     The foregoing is a summary and thus contains, by necessity, simplifications, generalizations and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the present invention, as defined solely by the claims, will become apparent in the non-limiting detailed description set forth below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be better understood, and its numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings. 
     FIG. 1A is a block diagram of an exemplary router. 
     FIG. 1B is a block diagram of a network including a number of the routers of FIG.  1 A. 
     FIG. 2 is a block diagram of the signal paths and functional blocks of the router of FIG.  1 A. 
     FIG. 3 is a block diagram of the control paths of the router of FIG.  1 A. 
     FIG. 4 illustrates the major components of one of the line cards. 
     FIG. 5 illustrates a view of a switching matrix that includes clock/data recovery units and connections to the line cards. 
     FIG. 6 illustrates a standard frame of the synchronous optical network protocol. 
     FIG. 7 illustrates a processor in accordance with an embodiment of the present invention. 
     FIG. 8 illustrates a concatenation scheme in accordance with an embodiment of the present invention. 
     The use of the same reference symbols in different drawings indicates identical items unless otherwise indicated. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following is intended to provide a detailed description of an example of the invention and should not be taken to be limiting of the invention itself. Rather, any number of variations may fall within the scope of the invention which is defined in the claims following the description. 
     In addition, the division of the detailed description into separate sections is merely done as an aid to understanding and is in no way intended to be limiting. 
     An Exemplary Network Element 
     FIG. 1A illustrates a router  100 . Router  100  includes an input/output section  110 , a node controller  120 , and a switching matrix  130 . Node controller  120  contains, for example, real time software and intelligent routing protocols (not shown). Router  100  supports interfaces including, but not limited to, optical signal interfaces (e.g., SONET), a user interface module  150 , and a management system  160 . Internal input signals  170  and internal output signals  180  may be electrical or optical in nature. 
     FIG. 1B illustrates a network  190  that includes a number of nodes, network nodes  195 ( 1 )-(N). One or more of network nodes  195 ( 1 )-(N) can be a router such as router  100 . Network  190  can thus support the automatic provisioning, testing, restoration, and termination of virtual paths (exemplified by a virtual path  191 ) over a physical path (exemplified by a physical path  192 ) from one of network nodes  195 ( 1 )-(N) to another of network nodes  195 ( 1 )-(N). 
     In one embodiment, there are at least three types of processors in a router  100 . The lowest level, level-3, resides on the line card and is responsible for all real time aspects of the processing of the physical protocol (e.g., SONET). In a SONET implementation, every level-3 processor is responsible for a single optical signal (e.g., an OC-48 signal) and, via a protocol processor, performs all required SONET/SDH section and line termination functions. The fast response time required from the level-3 processor makes a firmware implementation preferable. The firmware, which may be written in the “C” or “C++” programming languages, assembler, or other programming language, is preferably optimized for low latency and resource efficiency. Higher-level processing is implemented on a separate module, the shelf processor module, which is shared by several line cards. 
     The second level of processors, level-2, reside on a shelf and main matrix processor modules. The software on the shelf processor module is responsible for managing and controlling line cards. Only half the line cards supported are active at any one time in order to support 1+1 protection. A level-2 processor deals with tasks that require a reasonable response time (for example, on the order of milliseconds), but have no direct impact on the data path. In other words, missed events, such as hardware interrupts, do not result in bit errors. Some of the functions handled by the shelf processor include the periodic collection of maintenance data from the line cards, receiving and processing periodic keep-alive messages from those cards, shelf startup and configuration, proxy management, and other related functions. 
     The third processor level, level-1, resides on a system processor module and provides system-wide management and control services. In one embodiment, there are preferably two fully synchronous copies of the level-1 processor in the system, both of which are simultaneously active and, through a dedicated and redundant high-speed link, keep their run-time and stored databases fully synchronized. One of the two processors is designated the master and is responsible for all level-1 processing. An update message is sent to the second processor whenever a change is made to the database and before that change is effected. A periodic keep-alive mechanism allows either copy of the system controller to detect failures on the other copy. 
     Router  100  provides yet another type of processor, referred to herein as a route processor. Such a processor is dedicated to the path/route discovery and restoration functions. The route processor is responsible for receiving failure indications from the line cards, calculating a new route for failed connections, and sending reconfiguration requests to all affected nodes, including its own. 
     Hardware Architecture 
     In one embodiment, router  100  can be used, for example, as SONET/SDH line terminating equipment (LTE) capable of terminating the Section and Line overheads of received OC-48 signals, and cross-connects those signals according to provisioned input-output mappings. Some of the terminated signals can optionally be protected using any of the common protection schemes (1+1, 1:1, and 1:N). Overhead processing and generation is performed on the line card by a protocol processor. This protocol processor handles all aspects of the SONET protocol, including framing, insertion and extraction of embedded data channels, error checking, AIS detection, pointer processing, clock recovery, multiplexing/duplexing, and similar duties. 
     Signal Path 
     FIG. 2 is a block diagram of signal paths  200  within router  100 . The primary signal paths in router  100  include one or more groups exemplified by groups  210 ( 1 )-(N), group matrices  212 ( 1 )-(N), and a main matrix  214 . As depicted in FIG. 1A, groups  210 ( 1 )-(N), and group matrices  212 ( 1 )-(N) are shown as having receive and transmit sections. Groups  210 ( 1 )-(N) each include line cards  220 ( 1 , 1 )-( 1 ,N), through line cards  220 (N, 1 )-(N,N). Signals from line cards  220 ( 1 , 1 )-(N,N) are sent to the corresponding group matrix. In one embodiment, two sets of the group matrix cards, group matrices  212 ( 1 )-(N) and  216 ( 1 )-(N) are employed. Main matrix  214  is also mirrored in one embodiment by a redundant copy, a backup main matrix  218 , which together form switching matrix  130 . As shown in FIG. 2, the redundancy for group matrices  212 ( 1 )-(N) (i.e., group matrices  216 ( 1 )-(N)), is also provided on the transmit side. 
     It will be noted that the variable identifier “N” is used in several instances in FIG. 2 (and subsequent use of other variables, such as “m,” “x,” “k,” and others) to more simply designate the final element (e.g., group matrix  212 (N), line card  220 (N,N), and so on) of a series of related or similar elements (e.g., group matrices  212 ( 1 )-(N), line cards  220 ( 1 , 1 )-(N,N), and so on). The repeated use of such variable identifiers is not meant to imply a correlation between the sizes of such series of elements. The use of such variable identifiers does not require that each series of elements has the same number of elements as another series delimited by the same variable identifier. Rather, in each instance of use, the variable identified by “N” (or “m,” “x,” “k,” and others) may hold the same or a different value than other instances of the same variable identifier. For example, group matrix  212 (N) may be the tenth group matrix in a series of group matrices, whereas line card  220 (N,N) may be the forty-eighth line card in a series of line cards. 
     Using signal paths  200  as an example, data enters the system at one of line cards  220 ( 1 , 1 )-(N,N). It is at this point, in a SONET-based system, that the Section and Line overheads are processed and stripped off by a protocol processor (not shown). The extracted SONET/SDH payload envelope is then synchronized with the system clock and sent to two different copies of a local matrix, depicted as group matrices  212 ( 1 )-(N) and  216 ( 1 )-(N) in FIG.  1 A. In one embodiment, group matrices  212 ( 1 )-(N) and  216 ( 1 )-(N) are used mainly as 2:1 reduction stages that select one of two optical signals and pass the selected optical signal to switching matrix  130 . This allows the implementation of a variety of protection schemes (including 1:N, or 0:1) without having to use any additional ports on main matrix  214 . All protect signals are terminated at group matrices  212 ( 1 )-(N) and  216 ( 1 )-(N). In order to maximize bandwidth, it is preferable that only active signals be passed through to switching matrix  130 . 
     In one embodiment, switching matrix  130  is an errorless, rearrangeably non-blocking switching network. In one embodiment, switching matrix  130  is a 256×256 switching network that consists of three columns and 16 rows of 16×16 switching elements that allow any of their inputs to be connected to any of their outputs. A single copy of the matrix may be housed, for example, in a single rack that contains three shelves, one for each column (or stage) of the matrix. Each one of such shelves contains cards housing the 16 switching elements in each stage. The switching element itself includes, for example, a 16×16 crosspoint switch, with optical transceivers, and a microcontroller for controlling the crosspoint switch and providing operational feedback to the level-2 processor. Communications between the two processors may be carried, for example, over an Ethernet connection. The level-2 processor in turn communicates with the level-1 and route processors. 
     The switching elements in each matrix copy of the exemplary embodiment may be connected using fiber-optic cables, for example. While copper cabling may also be employed, such an option may not offer the speed and number of connections provided by an optical arrangement. After passing through the stages of switching matrix  130 , an optical signal may be routed to an I/O shelf that (optionally) splits the optical signal into two signals. One of the signals is sent to an active line card, while the other, when available, is sent to a backup card. 
     Line cards  220 ( 1 , 1 )-(N,N) receive optical signals from group matrices  212 ( 1 )-(N) and  216  ( 1 )-(N) which are in turn connected to two separate copies of the main matrix. Line cards  220 ( 1 , 1 )-(N,N) monitor both signals for errors and, after a user-defined integration period, switch to the backup signal if that signal exhibits better bit error rate (BER) performance than the prior active signal. This scheme, referred to herein as 1-plus-1, allows line cards  220 ( 1 , 1 )-(N,N) to select between the two copies of the group matrix without any level-1 or level-2 CPU intervention. This helps to ensure that such a switch can be made in 50 ms or less (per Bellcore&#39;s recommendations in GR-253 (GR-253:  Synchronous Optical Network  (SONET)  Transport Systems , Common Generic Criteria, Issue 2[Bellcore, Dec. 1995], included herein by reference, in its entirety and for all purposes)). The selected signal is then processed by the transmit section of the protocol processor, which inserts all required transport overhead bytes into the outgoing stream. 
     Regarding the signals described herein, both above and subsequently, those skilled in the art will recognize that a signal may be directly transmitted from a first logic block to a second logic block, or a signal may be modified (e.g., amplified, attenuated, delayed, latched, buffered, inverted, filtered or otherwise converted, etc.) between the logic blocks. Although the signals of the embodiments described herein are characterized as transmitted from one block to the next, other embodiments may include modified signals in place of such directly transmitted signals with the informational and/or functional aspect of the signal being transmitted between blocks. To some extent, a signal input at a second logic block may be conceptualized as a second signal derived from a first signal output from a first logic block due to physical limitations of the circuitry involved (e.g., there will inevitably be some attenuation and delay). Therefore, as used herein, a second signal derived from a first signal includes the first signal or any modifications to the first signal, whether due to circuit limitations or due to passage through other circuit elements which do not substantively change the informational and/or final functional aspect of the first signal. 
     Control Path 
     FIG. 3 illustrates a control path  300  of a router, such as router  100 . Control path  300  includes all non-payload-related flows within the system and the hardware and software necessary to the control of the signal paths illustrated in FIG.  2 . All major control flows are carried over an internal local area network (LAN), which is, for example, a collection of switched Ethernet segments. The structure of the internal LAN is hierarchical and can be created using a mixture of 10 Mbps and 100 Mbps Ethernet segments, for example. Higher-speed segments (e.g., gigabit Ethernet) can be used as well. 
     Groups 
     At the bottom of the hierarchy is what is referred to herein as a group matrix, or a Group Ethernet Repeater in a system using Ethernet communications, and depicted in FIG. 3 as group matrices  212 ( 1 )-(N) and  216 ( 1 )-(N). Each one of group matrices  212 ( 1 )-(N) and  216 ( 1 )-(N), also referred to herein as a hub, a repeater, or concentrator, is a physical layer device and preferably supports a star network topology, such as the IEEE 802.3 10BASE-T networking standard. The redundant connections from line cards  220 ( 1 , 1 )-(N,N) in each of groups  310 ( 1 )-(N) are connected to two repeaters that reside on two separate copies of the group matrix module. Preferably, each one of line cards  220 ( 1 , 1 )-(N,N) supports two network ports (e.g., 10BASE-T Ethernet ports). The two sets of four signals from each port pass through a relay that selects one of them for connection to the LAN for purposes of redundancy. Groups  310 ( 1 )-(N) represent the first layer of the control bus hierarchy. Group matrices  212 ( 1 )-(N) and  216 ( 1 )-(N) are each controlled by a shelf processor (not shown, for the sake of clarity) and communicate with one of the shelf switches described below via LAN connections. 
     Shelf Ethernet Switch 
     FIG. 3 also illustrates certain features of router  100  pertaining to the relationship between shelf switches  320 ( 1 )-(N) and  321 ( 1 )-(N), and groups  310 ( 1 )-(N). Groups  310 ( 1 )-(N) are again shown, with regard to the control functions thereof. In this depiction of groups  310 ( 1 )-(N), line cards  220 ( 1 , 1 )-(N,N) are shown as being attached to networking devices, indicated here as group matrices. Group matrices  212 ( 1 )-(N) and  216 ( 1 )-(N) may be, for example, multi-port Ethernet hubs running at 10 Mbps. Each of line cards  220 ( 1 , 1 )-(N,N) feed signals into two of group matrices  212 ( 1 )-(N) and  216 ( 1 )-(N). For example, line card  220 ( 1 , 1 ) feeds received information to group matrices  212 ( 1 ) and  216 ( 1 ). Group matrices  212 ( 1 )-(N) and  216 ( 1 )-(N) each feed a signal into shelf switches  320 ( 1 )-(N) and  321 ( 1 )-(N) of FIG.  2 . Shelf switches  320 ( 1 )-(N) and  321 ( 1 )-(N) are each controlled by a shelf processor (not shown for the sake of clarity) and communicate with one of the system switches (not shown, for the sake of clarity). 
     Shelf switches  320 ( 1 )-(N) and  321 ( 1 )-(N) are the next higher level of the control hierarchy in router  100 , and are located on the shelf processor module (exemplified by line racks ( 330 ( 1 )-(N)). Each copy of shelf switches  320 ( 1 )-(N) and  321 ( 1 )-(N) interconnects six connections from the three groups in each shelf, another connection from the shelf processor, and one connection from system switch  340  (and  341 ). Shelf switches  320 ( 1 )-(N) and  32 ( 1 )-(N) can be implemented, for example, using an 8-port Ethernet configured to handle 10 Mbps Ethernet traffic and a single-port, dual-rate switch (e.g., 10 Mbps/100 Mbps Ethernet). 
     System Switch 
     The next level of the hierarchy is the system switch, of which there are two copies in each router. These are shown as system switches  340  and  341  in FIG.  3 . This fully redundant scheme prevents failures on one switch from taking down the entire control bus. In one embodiment, a system switch manages connections from the following sources: 
     1. High-speed connection(s) from shelf switches  320 ( 1 )-(N) and  321 ( 1 )-(N); 
     2. High-speed connection(s) to higher-level processors (e.g., redundant level-1processors  350  and  351 , and redundant route processors  360  and  361 ); and 
     3. High-speed connection(s) to matrix shelf processors  370 ( 1 )-(N) and  371 ( 1 )-(N) which, in turn, control matrix cards  380 ( 1 , 1 )-( 1 ,N)), located in main matrix racks  390 ( 1 )-(N). It will be noted that main matrix  214  includes matrix cards  380 ( 1 , 1 )-( 1 ,N), and that, more generally, main matrices  214  and  218  are included matrix racks  390 ( 1 )-(N). 
     System switches  340  and  341  are located in a management bay. As noted, the fully redundant switches manage connections from various router elements, such as I/O and matrix bays, level-1 processors, and route processors. Each of level-1 processors  350  and  351  and route processors  360  and  361  is preferably connected to system switches  340  and  341  using 100 Mbps Ethernet connections in a configuration that creates an expandable, efficient, and fully redundant control bus. 
     Physical Configurations and Modules 
     System Modules 
     Line Card 
     FIG. 4 illustrates the major components of one of line cards  220 ( 1 , 1 )-(N,N), exemplified in FIG. 4 by a line card  400 . A line card integrates all the necessary hardware and software functions to properly terminate the physical layer. In a SONET implementation, a line card terminates the transport overhead (Section+Line) of a full duplex OC-48 signal. Other components on this card provide a redundant optical connection to the switch matrix, and a communication channel to other modules in the system. 
     Line card  400  receives optical signals from other network elements via a line-side optical receiver  405  and from the local router&#39;s system via a system-side optical receiver  406 . Each of these receivers implements an optical-to-electrical (O/E) conversion function. Line card  400  transmits optical signals to other network elements using a line-side optical transmitter  410  and to the group matrices using a system-side optical transmitter  411 . Each of these transmitters implements an electrical-to-optical (E/O) conversion function. It will be noted that line-side refers to the side of the line card coupled to other network elements and system-side refers to the side of the line card coupled to the group matrices. 
     Line-side optical receiver  405  is coupled to a protocol processor  420  which performs clock recovery multiplexing, demultiplexing, and SONET STE/LTE processing in both directions. Similarly, system-side optical receiver  406  is also coupled to protocol processor  420  to allow protocol processor  420  to receive optical signals. The processed electrical signals from protocol processor  420  are coupled to the transmitters  410  and  411 . The clock recovery functions are combined with demultiplexers and multiplexers to support reception and transmission of the optical data, respectively. The multiplexers serialize output data generated in protocol processor  420  by performing parallel-to-serial conversion on the parallel data. In contrast, de-multiplexers are used in protocol processor  420  to perform serial-to-parallel conversion on received data. 
     In order to add protection channels, line-side optical transmitter  410  is also coupled to a 1:2 broadcast unit  435 . To receive such optical signals, optical receiver  406  is also coupled to a 2:1 selector  436  in order to select the working channel before the optical signals leave the shelf and thus prevent the standby channel (also referred to herein as the protect channel) from using any bandwidth on switching matrix  130 . 
     Protocol processor  420  is coupled to a bus  445 . Protocol processor  420  interfaces the line card to two copies of the matrix in a 1+1 physical protocol. In a SONET implementation, protocol processor  420  provides both STE/LTE processing according to published industry standards. Also coupled to bus  445  are a memory  460  and a CPU  470 . Memory  460  should be fast enough for efficient operation of CPU  470 . 
     CPU  470  communicates with other of line cards  220 ( 1 , 1 )-(N,N) over a control bus (not shown) using a transceiver  480  that is coupled to CPU  470 . Transceiver  480 , is coupled to a transformer  485  which is coupled to a switch  490 . Switch  490  is coupled to the control bus. Switch  490  implements a 1:1 protection scheme for transceiver  480  and couples CPU  470  to two independent ports on the backplane (not shown). Each of the two ports connects to one copy of the hub of the group matrix. This allows the software on the line card to switch to the backup link when the software detects failures on the active link. 
     Preferably, CPU  470  includes numerous integrated peripherals including embedded SCC channels (e.g., in-band communications) and an Ethernet controller (for example, to support communications with other system modules). In one embodiment, CPU  470  provides an onboard communications processor module (not shown) that handles time-critical aspects of the protocols supported. 
     Hub 
     One or more hubs are also provided to support communication between the group matrices and system switches in router  100 . In an Ethernet communications environment, the hub&#39;s functions are carried out primarily by repeater interface controllers (RICs). Each RIC integrates the functions of a repeater, clock and data recovery unit (CDR), Manchester encoder/decoder, and transceiver. Each RIC has a set of registers that convey status information and allow a number of configuration options to be specified by the user using, for example, a microcontroller. 
     Shelf Processor Module 
     A shelf processor module provides, among other elements, a shelf processor and switch that interconnect the LAN segments from the groups and the shelf processor to a port on the shelf switch. 
     The shelf processor is responsible for the overall operation, management, and control of the shelf. 
     A network switch interconnects the lower speed inter-processor communication network segments in each shelf. In one embodiment, the network switch provides support for 10 Mbps and 100 Mbps segments. 
     In certain embodiments, the shelf processor is able to connect to two separate Ethernet segments. This can implement a 1:1 protection scheme that allows the shelf processor to recover from failures on the active segment by simply switching to the other segment. 
     System Switch 
     One embodiment of a system capable of interconnecting network segments in a switched configuration allows communications between shelf switches, higher-level (e.g., level-1) processors, and shelf-processors. In an Ethernet-based system, the system switch supports both 10 Mbps and 100 Mbps connections. The segments come from the shelf switching in the I/O shelf and the matrix switches, among others, and allow these elements to communicate. 
     Management Bay 
     The management bay can house, for example, the following modules: 
     1. Level-1 processors, or system controllers, and their associated storage devices; 
     2. Route processors; 
     3. Optional group and WAN cards; 
     4. System Ethernet switches; and 
     5. Synchronization modules. 
     All of the above modules are fully redundant and communicate with the rest of router  100  over redundant control buses. The placement of individual modules within the rack is not addressed in this document, since there are no architectural preferences, or restrictions, on such choices. 
     Level-1 Processor/System Controller 
     A system controller (also referred to herein as a level-1 processor) provides overall control of router  100 . The system controller also communicates with the system switches. The system controller includes a bus such as an all-purpose bus (APB), which in turn provides access to several bus and communications controllers. Among the controllers interfaced to the APB is a bus bridge, a peripheral interface, and an I/O interface. The I/O interface may provide functionality such as 10 Mbps/100 Mbps Ethernet communications. The I/O interface also supports peripherals such as keyboards, mice, floppy drives, parallel ports, serial ports, and the like. The bus bridge allows communications between the system controller&#39;s processor and other devices. The peripheral interface allows communications with peripherals such as hard disks. The system controller performs various functions, such as communicating with the route processor(s) to determine how the matrix should be configured, managing the router&#39;s resources, and similar duties. 
     APB may also be connected to a dual-channel serial communication controller (SCC), for example, which can be used to communicate with one or more remote Operations Systems (OS) using, for example, the X.25 protocol. For more OS links and higher link speeds, the user can optionally install one or more WAN Interface Modules in the management bay. Such modules, which preferably handle all real-time aspects of the OS link, including layer-2 of the OSI stack, communicate with the system controller. 
     Main Matrix Bay 
     Switching matrix  130  is based on a rearrangeably non-blocking switching matrix and can consist, for example, of switch nodes arranged in a staged array. For example, switching matrix  130  configured as a 256×256 switching matrix consists of  48  nodes arranged in an array of 16 rows by 3 columns, with each column containing one stage. All  48  nodes in the switch matrix are substantially similar. Each node is preferably a crossbar device, such as a 16×16 crossbar device that allows any of its 16 inputs to be connected to any of its 16 outputs, regardless of the crossbar&#39;s current state. 
     FIG. 5 illustrates a simplified view of switching matrix  130 , including connections to the line cards. The depiction of switching matrix  130  in FIG. 5 shows certain other details, such as clock/data recovery units (CDRs)  500 ( 1 , 1 )-( 6 , 256 ) and line cards  510 ( 1 , 1 )-( 16 , 16 ). A CDR recovers clock and data information from a serial bitstream by recovering the clocking signal from the incoming bitstream (e.g., using a phase-locked loop (PLL)), and then recovering the data using the clock thus recovered. 
     It will be noted that line cards  510 ( 1 , 1 )-( 16 , 16 ) correspond loosely to line cards  220 ( 1 , 1 )-(N,N), as depicted in FIG.  2 . It will also be noted that line cards  510 ( 1 , 1 )-( 16 , 16 ) are each shown as being divided into a receive section and a transmit section as shown in FIG. 5, again in a fashion similar to that depicted in FIG.  2 . Also depicted in FIG. 5 are switch nodes  520 ( 1 , 1 )-( 16 , 3 ) and a switching matrix control circuit  530 . More generically, the control function represented by switching matrix control circuitry  530  is depicted in FIG. 3 as matrix shelf processors  370 ( 1 )-(N) and  371 ( 1 )-(N). As previously noted, switch nodes  520 ( 1 , 1 )-( 16 , 3 ) and their related CDRs are divided into three stages, which are depicted in FIG. 5 as matrix first stage  540 , matrix center stage  550 , and matrix third stage  560 . It will be noted that matrix first stage  540 , matrix center stage  550 , and matrix third stage  560  correspond to the matrix stages represented by switch nodes  1100 ( 1 , 1 )-( 16 , 1 ), switch nodes  1100 ( 1 , 2 )-( 16 , 2 ), and switch nodes  1100 ( 1 , 3 )-( 16 , 3 ). It will also be noted that the transmit side of line cards  510 ( 1 , 1 )-( 16 , 16 ) each include CDR functionality. 
     SONET Frame 
     FIG. 6 illustrates a standard frame of the synchronous optical network (SONET) protocol, exemplified here by a SONET frame  1500 . SONET frame  1500  is divided horizontally into ninety columns and is divided vertically into nine rows. The first three columns of SONET frame  1500  contain overhead bytes used for framing, communications, and other purposes. The remaining 87 columns contain data and are collectively referred to as payload. The overhead bytes include an A 1  byte  1502 , an A 2  byte  1504 , a J 0 /Z 0  byte  1506 , a B 1  byte  1510 , an E 1  byte  1512 , an F 1  byte  1514 , a D 1  byte  1520 , a D 2  byte  1522 , a D 3  byte  1524 , an H 1  byte  1530 , an H 2  byte  1532 , an H 3  byte  1534 , an H 4  byte  1536 , a B 2  byte  1540 , a K 1  byte  1542 , a K 2  byte  1544 , a D 4  byte  1550 , a D 5  byte  1551 , a D 6  byte  1552 , a D 7  byte  1553 , a D 8  byte  1554 , a D 9  byte  1555 , a D 10  byte  1556 , a D 11  byte  1557 , a D 12  byte  1558 ,an S 1 /Z 1  byte  1570 , an M 1 /Z 2  byte  1572 , and an E 2  byte  1574 . Also included in SONET frame  1500  is payload data, represented here by payload bytes  1590 - 1598 . It will be noted that each of payload bytes  1590 - 1598  includes 87*48 bytes of data for an OC-48 SONET frame (except payload bytes  1593 , which includes 86*48 bytes of data (due to the existence of H 4  byte  1536 )). 
     Concatenated Payloads 
     For a SONET system to function as an OC-192 system, data payloads are typically concatenated for transmission. Accordingly, integrated circuits, such as ASICs, are coupled to transmit the data. 
     FIG. 7, as more fully described below, shows a processor in accordance with an embodiment of the invention, including pin descriptions allowing the processor to function as either a master or a slave processor in a line card. FIG. 8 demonstrates several processors, such as the processor shown in FIG. 7, coupled in a manner consistent with an embodiment of the present invention. 
     Referring now to Table 1, below, a typical STS SPE payload pointer for a SONET system is shown in bits  7  through  16 . The table shows bits seven through sixteen are designated either “I” for an increment or “D” for decrement. These bits are typically designated as the pointer value to indicate the offset between the pointer word and the first byte of the STS SPE. In a concatenated payload, in which more than one STS-1 is used to carry an SPE, these bits are used to carry a concatenation indicator in the second through the nth STS-1. Thus, the concatenation detection requires the detection of the pointer word value to serially pass from the nth STS-1 to the first STS-1 . 
     
       
         
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                 Byte 
               
               
                   
                   
                   
                 0 of 
               
               
                   
                   
                 H3 
                 pay- 
               
               
                 H1 byte 
                 H2 byte 
                 byte 
                 load 
               
               
                   
               
             
             
               
                 1 2  3  4 5 6 7 8 
                 9  10   11 12 13 14 15 16 
                 . . . 
                 . . . 
               
               
                 N|N|N|N|—|—|I|D 
                 I | D | I | D | I | D | I | D | 
                 Neg- 
                 Posi- 
               
               
                   
                   
                 ative 
                 tive 
               
               
                   
                   
                 Stuff 
                 Stuff 
               
               
                   
                   
                 Byte 
                 Byte 
               
               
                   
               
             
          
         
       
     
     The interconnected circuits shown in FIG. 8 allow a concatenated group of STS-1s in an STS-Nc to be dispersed across the processors  810 ,  812 ,  814  and  816 . Each of the STS-1s contain part of the STS-Nc SPE rather than individual STS-1 SPEs. 
     According to the GR-253 specification, the STS-1s contain concatenation indicators contained in payload pointers of the second through nth STS-1s in an STS-Nc. The concatenation indicators show that the second through nth STS-1s each contain part of the STS-Nc SPE. The STS-1 in the master processor  816  would not typically have a concatenation indicator, but holds a normal pointer word. STS-1s in processors  810 ,  812  and  814  each have pointer values shown in bits  7  through  16  set to all ones, with N-bits set to 1001, giving a pointer word value of:1001 XX11 11111111. The pointer word value appears in the H 1  and H 2  bytes through the nth STS-1s, commonly referred to as “slave channels.” 
     The GR-253 specification provides for concatenation detection by integrating the detection of the pointer word value over a number of frames. Accordingly, if a large concatenated signal is present, such as that required in an STS-192c payload, the integration data for each channel passes from integrated circuit to integrated circuit. 
     Referring to FIG. 7 in combination with Table 2, below, a communication processor in accordance with an embodiment supports OC-192. Accordingly, OC-192 support signals are communicated from a master processor to all of the slave processors attached thereto. Referring to FIG. 7, processor  700  determines whether it is a master or slave processor according to predetermined OC-192 support pins. The pins configure the ASIC  700  as in input or an output depending according to whether the particular ASIC is being operated in an OC-192 slave position or an OC-192 master position. External pins are used to specify to the device holding the master and slave processors the type of OC-192 position a particular ASIC processor occupies. Table 2 shows the configuration of pins indicating master and slave positions. 
     
       
         
               
             
               
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 OC-192 IO Pins on FIG. 7 
               
             
          
           
               
                 OC-192 
                 Pin Function 
                 Pin Function 
               
               
                 Pin Name 
                 when device is 
                 when device is 
               
               
                 (IO Type) 
                 OC-192 Master 
                 OC-192 Slave 
               
               
                   
               
               
                 RX_192C_DE 
                 This signal is a logical OR function 
                 This negative true signal is monitored 
               
               
                 TB 701 
                 which is connected commonly to four 
                 AND driven by slave processors. A 
               
               
                 (Bidir- 
                 or more ASIC devices in an OC-192c 
                 slave processor asserts this signal IF 
               
               
                 ectional) 
                 application and which is pulled up 
                 all 48 of its RLOP processors are 
               
               
                 (logical-OR) 
                 with a resistor on a circuit board. 
                 detecting a concatenation indication 
               
               
                   
                 Any device that wishes to assert this 
               
               
                   
                 signal as active should pull the signal 
                 in their H1 and H2 pointer bytes. An 
               
               
                   
                 down. Any device not asserting this 
                 active low monitored on this signal 
               
               
                   
                 signal will tristate its output driver. 
                 indicates to the slave processor that 
               
               
                   
                 This negative true signal is monitored 
                 an OC-192c concatenated signal is 
               
               
                   
                 only by the master processor. An 
                 present in the receive path. This 
               
               
                   
                 active low on this input indicates to 
                 signal is monitored by the slave 
               
               
                   
                 the master processor that an OC-192c 
                 device (instead of the internal 
               
               
                   
                 concatenated signal is present in the 
                 “assertion” signal that says drive this 
               
               
                   
                 receive path signal. 
                 pin active) to allow for proper actions 
               
               
                   
                 (This signal is necessary for the 
                 in the event that a particular slave 
               
               
                   
                 master processor to be able to 
                 processor has a failure (and ceases to 
               
               
                   
                 distinguish an OC-192c concatenated 
                 indicate concatenation within itself). 
               
               
                   
                 signal from an OC-48c concatenated 
               
               
                   
                 signal.) 
               
             
          
           
               
                 RX_192C_FAI 
                 This signal is a logical OR function which is connected commonly to each 
               
               
                 LB 703 
                 (four or more, typically) processor devices in an OC-192c application and 
               
               
                 (Bidir- 
                 which is pulled up with a resistor on the circuit board. Any device that wishes 
               
               
                 ectional) 
                 to assert this signal as active should pull the signal down. Any device not 
               
               
                 Logical OR) 
                 asserting this signal will tristate its output driver. 
               
               
                   
                 This signal is not specific to either master or slave device. All processor 
               
               
                   
                 devices have the capability to assert this signal and all processor devices 
               
               
                   
                 monitor this signal. A processor asserts this signal if RX_192C_DETB is 
               
               
                   
                 detected active AND one of the following conditions is detected in the RIS or 
               
               
                   
                 RLOP sections: LOACLK (Loss of activity on Clock), LOADAT (Loss of 
               
               
                   
                 activity on Data), OOF (Out of Frame), LOF (Loss of Frame), or LOP (Loss 
               
               
                   
                 of Pointer). Any processor that detects this signal active will insert Path AIS 
               
               
                   
                 in its transmit output stream onto the backplane. (for details on the errors that 
               
               
                   
                 will assert this signal and the action taken when it is asserted.) 
               
               
                   
                 Control bits in the RIS_CR control register used to inhibit/enable the 
               
               
                   
                 assertion conditions mentioned above also affect whether those conditions 
               
               
                   
                 affect this signal. 
               
             
          
           
               
                 TX_192C_DET 
                 This signal is a logical OR function 
                 This negative true signal is monitored 
               
               
                 B 705 
                 which is connected commonly to all 
                 AND driven by slave processors. A 
               
               
                 (Bidir- 
                 four processor devices in an OC-192c 
                 slave processor should assert this 
               
               
                 ectional) 
                 application and which is pulled up 
                 signal IF all 48 of its TLOP 
               
               
                 (logical OR) 
                 with a resistor on the PCB. Any 
                 processors are detecting a 
               
               
                   
                 device that wishes to assert this signal 
                 concatenation indication in their H1 
               
               
                   
                 as active should pull the signal down. 
                 and H2 pointer bytes. An active low 
               
               
                   
                 Any device not asserting this signal 
                 monitored on this signal indicates to 
               
               
                   
                 will tristate its output driver. 
                 the slave that an OC-192C 
               
               
                   
                 This negative true signal is monitored 
                 concatenated signal is present in the 
               
               
                   
                 only by the master processor. An 
                 transmit path signal. This signal is 
               
               
                   
                 active low on this input indicates to 
                 monitored by the slave device 
               
               
                   
                 the master Processor that an OC- 
                 (instead of the internal “assertion” 
               
               
                   
                 192C concatenated signal is present 
                 signal that says drive this pin active) 
               
               
                   
                 on the transmit path signal. 
                 to allow for proper actions in the 
               
               
                   
                 (This signal is necessary for the 
                 event that a particular slave processor 
               
               
                   
                 master processor to be able to 
                 has a failure (and ceases to indicate 
               
               
                   
                 distinguish an OC-192c concatenated 
                 concatenate within itself). 
               
               
                   
                 signal from an OC-48c concatenated 
               
               
                   
                 signal.) 
               
             
          
           
               
                 TX_192C_FAI 
                 This signal is a logical OR function which is connected commonly to four 
               
               
                 LB 707 
                 devices in an OC-192c application and which is pulled up with a resistor on 
               
               
                 (Bidir- 
                 the circuit board. Any device that wishes to assert this signal as active should 
               
               
                 ectional) 
                 pull the signal down. Any device not asserting this signal will tristate its 
               
               
                 (Logical OR) 
                 output driver. 
               
               
                   
                 This signal is not specific to either master or slave device. All processor 
               
               
                   
                 devices have the capability to assert this signal and all devices monitor this 
               
               
                   
                 signal. A processor asserts this signal if TX_192C_DETB is detected active 
               
               
                   
                 AND one of the following conditions is detected in the TIS or TLOP sections: 
               
               
                   
                 LOACLK (Loss of activity on Clock), LOADAT (Loss of activity on Data), 
               
               
                   
                 OOF (Out of Frame), LOF (Loss of Frame), or LOP (Loss of pointer). Any 
               
               
                   
                 processor that detects this signal active will insert Path AIS in its transmit 
               
               
                   
                 output stream onto the SONET line. 
               
               
                   
                 Control bits in the TIS_CR control register used to inhibit/enable the assertion 
               
               
                   
                 conditions mentioned above also affect whether those conditions affect this 
               
               
                   
                 signal. 
               
               
                 FB_FAILB 
                 This negative true input pin is not specific to either master or slave mode. 
               
               
                 709 (Input) 
                 This pin is received into the Receive Input section (RIS) of the processor. In 
               
               
                   
                 CFG-192 mode, this input is used to indicate (when asserted) that the source 
               
               
                   
                 processor OC-192 front end has detected an input line error and that the 
               
               
                   
                 Processor should reset its RLOP FIFOs and insert path AIS (in all 48 
               
               
                   
                 channels) on the backplane. In CFG-48 mode, this input is used as a line side 
               
               
                   
                 direct LOS (loss of signal) input from the optics module and indicates LOS 
               
               
                   
                 when asserted low. 
               
               
                 FRC_FRAME 
                 This function is not specific to either master or slave mode. This function is 
               
               
                 711 
                 received into the Receive Input Section (RIS) of the processor. This input is 
               
               
                 (Input) 
                 used to indicate that the processor should reset its framer and start frame 
               
               
                   
                 search again. This input is required to avoid the latency of the processor 
               
               
                   
                 detecting that it is out of frame after source processor has already detected 
               
               
                   
                 that it is out of frame. When the source processor detects a condition that 
               
               
                   
                 requires realignment of the frame position, it will assert this input into the 
               
               
                   
                 processor device to force the new frame alignment to be recognized. 
               
               
                 FRAME_LOC 
                 This function is not specific to either master or slave mode. This signal is an 
               
               
                 713 
                 output from the Transmit Output section (TOS) and is used by the source 
               
               
                 (Output) 
                 processor to know the frame location. This output is provided to the source 
               
               
                   
                 processor so that a full framer is not required on the source processor input 
               
               
                   
                 port that is receiving the processor transmit output data. This output is 
               
               
                   
                 155 MHz synchronous and will overlay on the CFG-48 AMCC_READ function. 
               
             
          
           
               
                 CFG[2:0] 
                 Tied high (‘111’) on circuit board. 
                 Tied high (‘100’ −&gt; ‘110’) on PC 
               
               
                 715 (Input) 
                   
                 board. (Three unique slave positions) 
               
               
                 RX_WEN, 
                 These two pins are used to 
                 These two pins are used to 
               
               
                 717 
                 synchronously control writing of the 
                 synchronously control writing of all 
               
               
                 RX_WSYNC, 
                 receive path FIFO&#39;s (across four 
                 48 RLOP FIFO&#39;s in the receive path 
               
               
                 719 (Bidir- 
                 processor chips) when an OC-192c 
                 of a processor configured as CFG- 
               
               
                 ectional) 
                 signal is present in the receive path. 
                 192-S. These pins are configured as 
               
               
                   
                 These pins are configured as output 
                 inputs and are received from the 
               
               
                   
                 only from the CFG-192-M device 
                 CFG-192-M device. The slave 
               
               
                   
                 and carry the values of the 
                 device only uses these inputs to 
               
               
                   
                 RLOP{47} FIFO write control 
                 control its 48 RLOP FIFO&#39;s when an 
               
               
                   
                 signals. (RLOP{47} is the master 
                 OC-192c concatenated signal is 
               
               
                   
                 channel processor for an OC-192c 
                 present. For any (receive path) signal 
               
               
                   
                 signal.) RX_WEN==Write Enable 
                 other than OC-192c, these inputs are 
               
               
                   
                 and RX_WSYNC==Write Sync. 
                 ignored. See description in box to the 
               
               
                   
                 These pins are asserted 
                 left pin function. These pins are 
               
               
                   
                 synchronously with respect to the 
                 received synchronously with respect 
               
               
                   
                 6.48 MHz RI_CLK6 clock signal that 
                 to the local RI_CLK6 clock in each 
               
               
                   
                 is derived from the RI_CLK155 input 
                 of the slave devices. 
               
               
                   
                 clock. 
               
               
                 RX_REN, 
                 These two pins are used to 
                 These two pins are used to 
               
               
                 721 
                 synchronously control reading of the 
                 synchronously control reading of all 
               
               
                 RX_RSYNC 
                 receive path FIFO&#39;s (across four 
                 48 RLOP FIFO&#39;s in the receive path 
               
               
                 723 
                 processor chips) when an OC-192c 
                 of a processor configured as CFG- 
               
               
                 (Bidir- 
                 signal is present in the receive 
                 192-S. These pins are configured as 
               
               
                 tional) 
                 path. 
                 inputs and are received from the 
               
               
                   
                 These pins are configured as output 
                 CFG-192-M device. The slave 
               
               
                   
                 only from the CFG-192-M device 
                 device only uses these inputs to 
               
               
                   
                 and carry the values of the 
                 control its 48 RLOP FIFO&#39;s when an 
               
               
                   
                 RLOP{47} FIFO read control 
                 OC-192c concatenated signal is 
               
               
                   
                 signals. (RLOP{47} is the master 
                 present. For any (receive path) signal 
               
               
                   
                 channel processor for an OC-192c 
                 other than OC-192c, these inputs are 
               
               
                   
                 signal.) RX_REN==Read Enable 
                 ignored. See description in box to the 
               
               
                   
                 and RX_RSYNC==Read Sync. 
                 left pin function. These pins are 
               
               
                   
                 These pins are asserted 
                 received synchronously with respect 
               
               
                   
                 synchronously with respect to the 
                 to the local RO_CLK6 clock in each 
               
               
                   
                 6.48 MHz RO_CLK6 clock signal that 
                 of the slave devices. 
               
               
                   
                 is derived from the RO_CLK155 
               
               
                   
                 input clock. 
               
               
                 TX_WEN, 
                 These two pins are used to 
                 These two pins are used to 
               
               
                 725 
                 synchronously control writing of the 
                 synchronously control writing of all 
               
               
                 TX_WSYNC, 
                 transmit path FIFO&#39;s (across four 
                 48 TLOP FIFO&#39;s in the transmit path 
               
               
                 727 
                 processor chips) when an OC-192c 
                 of a processor device configured as 
               
               
                 (Bidir- 
                 signal is present in the transmit path. 
                 CFG-192-S. These pins are 
               
               
                 ectional) 
                 These pins are configured as output 
                 configured as inputs and are received 
               
               
                   
                 only from the CFG-192-M device 
                 from the CFG-192-M device. The 
               
               
                   
                 and carry the values of the 
                 slave device only uses these inputs to 
               
               
                   
                 TLOP{47} FIFO write control 
                 control its 48 TLOP FIFO&#39;s when an 
               
               
                   
                 signals. (TLOP{47} is the master 
                 OC-192c concatenated signal is 
               
               
                   
                 channel processor for an OC-192c 
                 present. For any (transmit path) 
               
               
                   
                 signal.) TX_WEN==Write Enable 
                 signal other than OC-192c, these 
               
               
                   
                 and TX_WSYNC==Write Sync. 
                 inputs are ignored. See description in 
               
               
                   
                 These pins are asserted 
                 box to the left pin function. These 
               
               
                   
                 synchronously with respect to the 
                 pins are received synchronously with 
               
               
                   
                 6.48 MHz TI_CLK6 clock signal that 
                 respect to the local TI_CLK6 clock in 
               
               
                   
                 is derived from the TI_CLK155 input 
                 each of the slave devices. 
               
               
                   
                 clock. 
               
               
                 TX_REN, 
                 These two pins are used to 
                 These two pins are used to 
               
               
                 729 
                 synchronously control reading of the 
                 synchronously control reading of all 
               
               
                 TX_RSYNC 
                 transmit path FIFO&#39;s (across four 
                 48 TLOP FIFO&#39;s in the transmit path 
               
               
                 731 
                 processor chips) when an OC-192c 
                 of a processor device configured as 
               
               
                 (Bidir- 
                 signal is present in the transmit path. 
                 CFG-192-S. These pins are 
               
               
                 ectional) 
                 These pins are configured as output 
                 configured as inputs and are received 
               
               
                   
                 only from the CFG-192-M device 
                 from the CFG-192-M device. The 
               
               
                   
                 and carry the values of the 
                 slave device only uses these inputs to 
               
               
                   
                 TLOP{47} FIFO read control signals. 
                 control its 48 TLOP FIFO&#39;s when an 
               
               
                   
                 (TLOP{47} is the master channel 
                 OC-192c concatenated signal is 
               
               
                   
                 processor for an OC-192c signal.) 
                 present. For any (transmit path) 
               
               
                   
                 TX_REN==Read Enable and 
                 signal other than OC-192c, these 
               
               
                   
                 TX_RSYNC==Read Sync. These 
                 inputs are ignored. See description in 
               
               
                   
                 pins are asserted synchronously with 
                 box to the left pin function. These 
               
               
                   
                 respect to the 6.48 MHz TO_CLK6 
                 pins are received synchronously with 
               
               
                   
                 clock signal that is derived from the 
                 respect to the local TO_CLK6 clock 
               
               
                   
                 TO_CLK155 input clock. 
                 in each of the slave processor 
               
               
                   
                   
                 devices. 
               
               
                 RL_RST, 
                 These pins are configured as outputs 
                 These pins are configured as inputs 
               
               
                 733 
                 of the OC-192 master processor. 
                 by processors configured as CFG- 
               
               
                 RL_SPAIS, 
                 These signals are provided to allow 
                 192-S. The value received on these 
               
               
                 735 
                 synchronous control of all of the 
                 pins (from the master device) is OR&#39;d 
               
               
                 RL_IDLE 
                 RLOPs not located in the CFG-192- 
                 internally with the corresponding bit 
               
               
                 737 
                 M processor. The value driven on 
                 values out of the local GL_CR1 
               
               
                 (Bidir- 
                 these signals is the (maskable) value 
                 register. These inputs are used to 
               
               
                 ectional) 
                 of the corresponding bit in the 
                 allow the master processor to control 
               
               
                   
                 GL_CR1 register OR the 
                 all of the RLOP&#39;s not within its own 
               
               
                   
                 corresponding value in the 
                 device for global software control or 
               
               
                   
                 RL_CR{47} register if the 
                 for global OC-192c signal 
               
               
                   
                 RX_192C_DETB signal is active. 
                 management. Refer to descriptions of 
               
               
                   
                 RL_RST==Reset, RL_SPAIS==Send 
                 the GL_CR1 register and the 
               
               
                   
                 Path AIS and RL_IDLE==idle. Refer 
                 RL_CR{47} register for more detail 
               
               
                   
                 to descriptions of the GL_CR1 
                 regarding the usage and actions 
               
               
                   
                 register and the RL#CR{47} register 
                 performed by these signals. 
               
               
                   
                 for more detail regarding the usage 
               
               
                   
                 and actions performed by these 
               
               
                   
                 signals. These signals are driven 
               
               
                   
                 synchronously with the CPU_CLK 
               
               
                 TL_RST, 
                 These pins are configured as outputs 
                 These pins are configured as inputs 
               
               
                 739 
                 of the OC-192 master processor. 
                 by processors configured as CFG- 
               
               
                 TL_SPAIS, 
                 These signals are provided to allow 
                 192-S. The value received on these 
               
               
                 741 
                 synchronous control of all of the 
                 pins (from the master device) is OR&#39;d 
               
               
                 TL_IDLE 
                 TLOPs not located in the CFG-192- 
                 internally with the corresponding bit 
               
               
                 743 
                 M processor. The value driven on 
                 values out of the local GL_CR1 
               
               
                 (Bidir- 
                 these signals is the (maskable) value 
                 register. These inputs are used to 
               
               
                 ectional) 
                 of the corresponding bit in the 
                 allow the master processor to control 
               
               
                   
                 GL_CR1 register OR the 
                 all of the TLOP&#39;s not within its own 
               
               
                   
                 corresponding value in the 
                 device for global software control or 
               
               
                   
                 TL_CR{47} register if the 
                 for global OC-192c signal 
               
               
                   
                 TX_192C_DETB signal is active. 
                 management. Refer to descriptions of 
               
               
                   
                 TL_RST==Reset, TL_SPAIS==Send 
                 the GL_CR1 register and the 
               
               
                   
                 Path AIS and TL_IDLE==Idle. Refer 
                 TL_CR{47} register for more detail 
               
               
                   
                 to descriptions of the GL_CR1 
                 regarding the usage and actions 
               
               
                   
                 register and the TL_CR{47} register 
                 performed by these signals. 
               
               
                   
                 for more detail regarding the usage 
               
               
                   
                 and actions performed by these 
               
               
                   
                 signals. These signals are driven 
               
               
                   
                 synchronously with the CPU_CLK 
               
               
                   
               
             
          
         
       
     
     Referring now to FIG. 8, an embodiment of the present invention shows a configuration of four processors interconnected to form an OC-192 processor card. 
     OC-192c concatenated streams are detected by use of the RX — 192C_DETB  701  shown in FIG. 7, and TX — 192C_DETB  705  wires for the receive path and transmit path respectively. These logical OR detection signals are monitored by all four devices but may only be driven by the three slave devices. A slave processor should drive one of the 192c detection lines if all of the respective LOP&#39;s (receive or transmit) within that device are indicating concatenation. This scheme is adopted such that if one of the slave processors fails (and ceases to see concatenation in all 48 of its LOP&#39;s) then one of the good slaves will still be asserting the 192c detection line, and 192c detection is not lost due to the failure of any one slave processor. 
     The master processor also drives control information to the downstream devices. The control signals are only observed at the slave processors  810 ,  812  and  814  if an OC192c signal is present. Thus, for example, if master processor is processor  816 , slave processors  810 ,  812  and  814  determine that an OC-192c signal is present if they detect that the input side of their {RX,TX} — 192C_DETB  701  and  705  signal is active low. The control signals driven from the master processor  816  to the slave processors  810 ,  812 , and  814  are designed to synchronize the reading and writing of the FIFO&#39;s across all four processors (192 FIFO&#39;s). Additionally, global control signals (not shown) from the master processors GL_CR 1  (Global Control Register #1) are driven to the slave devices  810 ,  812 , and  814  such that only one Global Control Register is needed to perform certain global functions. 
     Referring now to FIG. 8, a configuration in accordance with an embodiment of the present invention shows a concatenated group of STS-1s in an STS-Nc dispersed across several integrated circuits  810 ,  812 ,  814  and  816 . Each of the STS-1s contain part of the STS-Nc SPE rather than individual STS-1 SPEs. Integrated circuit  810  is the first integrated circuit. Although FIG. 8 shows four integrated circuits, the number of circuits is not limited according to an embodiment of the invention. The four integrated circuits are, according to one embodiment, application specific integrated circuits (ASICs) present on one communication module. Each of the four integrated circuits are coupled via a concatenation wire  850 . Instead of passing the concatenation pattern shown in the H 1  and H 2  bytes from integrated circuit to integrated circuit, the method according to an embodiment of the present invention uses wire  850  to detect concatenation for all integrated circuits simultaneously. 
     The method applies to one or more integrated circuits that are concatenated. For example, if there are N integrated circuits, such as ASICs on a module and M STS-1s, and the division of STS-1s per ASIC is K, the master ASIC, or the integrated circuit hold the first STS-1 includes an input coupled to a wire, such as wire  850 . The wire is driven as an input by any N−1 integrated circuits on the module. The N−1 integrated circuits drive the wire low when all K STS-1s internally are detected to be concatenation slaves. If not all the channels are slaves, the wire  850  tristates. Accordingly, the wire  850  is an active low if any one of the N−1 integrated circuits detects all K channels as “slaves.” 
     In one embodiment, the wire  850  includes a pullup resistor to hold a signal high. For example, if each of the N−1 integrated circuits are tristated, the pullup resistor would be required to prevent the high signal from falling below a high signal level. 
     In one embodiment, the wiring of the integrated circuits causes a detection of multiple STS-1s if any of the N−1 integrated circuits drives the concatenation detection wire low and all channels other than the first channel on circuit  816  are concatenation slaves. For example, if an OC-192 STS-192 is transmitted using four ASICs with 48 channels per ASIC, according to the wiring scheme, M=192, N=4 and K=48, with one of the N integrated circuits being a master, if any one of the non-master integrated circuits detects all slaves on its integrated circuit, that one integrated circuit declares that all other channels on the non-slave integrated circuits are slaves and an STS-192c is declared. 
     According to an embodiment, the declaration by the one slave integrated circuit causes control signals to adjust to the STS-192c declaration. Further, according to an embodiment, the wire  850  requires only one external pin on an integrated circuit to perform the concatenation detection. 
     According to a further embodiment, the number N, identifying the number of integrated circuits coupled for concatenated payloads includes a number appropriate for detection of concatenation of different STS sized modules and integrated circuits, including those required for OC768 and OC-3072 
     While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this invention.