Synchronisation in communication systems

Abstract

A method and a communication bus are provided having nodes. Each of the nodes includes a transmitting element to transmit data to another node on the bus, and a receiving element to receive information from another node on the bus. A communication channel is between the transmitting and receiving elements within each node, a transmitter state machine logic controls the synchronisation of the transmitting element, and a receiving state machine logic to control the synchronisation of the receiving element. A storage area maintains the status of synchronisation of the bus. Communication data is synchronised via a bus connecting first and second nodes. A plurality of encoded bytes, each encoded byte represented as a 10 bit code, is transmitted from the first node. The second node receives and decodes the bytes, where any decoding errors in a byte are detected. A synchronised status is indicated.

1 . A communication bus having nodes that are linked by communications channels, wherein a first set of said channels transfers information in one direction while a second set of channels transfers information in the opposite direction, each of said nodes comprising: 
 a transmitting element for transmitting data to another node on said bus;    a receiving element for receiving information from another node on said bus;    a communication channel between said transmitting and receiving elements within each node;    transmitter state machine logic for controlling the synchronisation of said transmitting element;    receiving state machine logic for controlling the synchronisation of said receiving element; and    a storage area for maintaining the status of synchronisation of said bus.    
     
     
         2 . A method of synchronising data communication via a bus connecting first and second nodes comprising: 
 transmitting from the first node a plurality of encoded bytes, each encoded byte represented as a 10 bit code;    receiving and decoding said bytes at the second node, whereby any 8b10b decoding errors in a byte is detected; and    indicating a synchronised status for the bus based on the detection of received encoded bytes which do not contain 8b10b decoding errors.    
     
     
         3 . A method of synchronising data communications according to  claim 2 , wherein the number of consecutive bytes received at the second node with no 8b10b decoding errors is counted, and the synchronised status of the bus is indicated when said number reaches a predetermined value.  
     
     
         4 . A method of synchronising data communication according to  claim 2 , wherein the plurality of 8b10b encoded bytes are transmitted in blocks of more than one byte and wherein the number of consecutive blocks received at the second node with no decoding errors is counted, and the synchronised status of the bus is indicated when said number reaches a predetermined value.  
     
     
         5 . A method according to  claim 2 , wherein the step of transmitting data from the first node is controlled responsive to the indicated synchronised status determined at the second node.  
     
     
         6 . A method according to  claim 5 , wherein, on detection of a synchronised status, data is transmitted in a frame structure and on detection of an unsynchronised state ˜dle codes are transmitted.  
     
     
         7 . A method according to  claim 2 , wherein each of said nodes is implemented using an ASIC or FPGA (Field Programmable Gate Array) or PLC (Programmable Logic Device) or processor and said each of said communication channels connecting said nodes using a LVDS point-to-point link.