Sepam - HV/MV Protection and control units (ENG) - Trinet

MERLIN GERINMERLIN GERINMERLIN GERINMERLIN GERINMERLIN GERINMERLIN GERINMERLIN GERINAppendixJbus protocolDescription of exchangesJbus protocol may be used to read or write oneor more bits, one or more words, the contentof the event counter or the contents of the diagnosiscounters.14 functions are available:c reading of n output or internal bits,c reading of n input bits,c reading of n output or internal words,c reading of n input words,c writing of 1 bit,c writing of 1 word,c high-speed reading of 8 bits,c diagnosis of exchanges,c reading of the event counter,c writing of n bits,c writing of n words.replyrequestmasterslave slave slaveExchanges are initiated by the master and include a request by the master and a replyby the slave (Sepam 2000). Requests by the master are either addressed to a given Sepamidentified by its number in the first byte of the request frame, or addressed to allthe Sepam 2000s (broadcasting).masterbroadcastingslave slave slaveBroadcast commands are necessarily writing commands. No replies are transmitted by theSepam 2000s.masterrequestreplyslaveIt is not necessary to have a detailed knowledge of the protocol unless the master is a centralcomputer which requires the corresponding programming. All Jbus exchanges include2 messages: a request by the master and a reply by the Sepam 2000.All the frames that are exchanged have the same structure.Each messages or frame contains 4 types of data:slavenumberfunctioncodedatazoneCRC 16check zonec slave number (1 byte): this indicates the receiving Sepam 2000 (0 to FFh). If it isequal to zero, therequest concerns all the slaves (broadcasting) and there is no reply message,c function code (1 byte): this is used to select a command (read, write, bit, word)and t ocheck that the reply is correct,c data zone (n bytes): this zone contains theparameters relating to the function: bit address, word address, bit value, word value,number of bits, number of words,c check zone (2 bytes): this zone is used to detect transmission errors.Synchronization of exchangesAny character that is received after a silence of more than 3 characters is consideredas the beginning of a frame. A silence of at least 3 characters must be left on the linebetween two frames.Example: at 9600 bauds, this time is equal to approximately 3 milliseconds.38 Jbus/Modbus communication