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

Request framethis codeis used to selectthe availablecommandsinformation requiredfor the request bitor word address,bit or word value,number of bits or wordswhen the message is receivedby the slave, the slave readsthe check word and acceptsor refuses the message0 à FFhcodefonctioninformations CRC 161 octet 1 octet N octets 2 octetsReply frameaddress of bits or words readvalue of bits or words readnumber of bits or words0 to FFhfunction codefonction codeinformation CRC 161 byte 1 byte N bytes 2 bytesChecking of messages received by Sepam 2000When the master transmits a request, after havingindicated:c the lave number,c the function code,c the function parameters,it computes and transmits the contents of the checkword (CRC 16). When the slave receives the requestmessage, it stores it, computes the CRC 16 andcompares it with the CRC 16 received.If the message received is incorrect(CRC 16s not equal), the slave does not reply.If the message received is correct but the slave cannotprocess it (wrong address, incorrect data, ...),it sends an exception reply.masterContents of an exception replyfunction code (Y) receivedand MS bit at 1slave n°CRC 16datafunctionslaveCRC 16calculationcomparison of CRC 16exception code01. unknown function code02. incorrect address03. incorrect data04. PLC not ready07. not acknowledged0 to FFh 1Y hCRC 161 byte (8 x h) 1 byte2 bytesExample :c request01 09 00 00 00 00CRC 16c reply01 : unknown function code01 89 01CRC 16Jbus/Modbus communication39