Parker EME RS232 & RS485 ñ interface recordI11 T11 192-120101 N6 - March 2004 795.2 Binary recordThe binary record with block securing is based on 5 different telegrams:! 2 request telegrams which the control sends to Compax3 and! 3 response telegrams which Compax3 returns to the control.Telegram layoutBasic structure:Start code Address Number of data bytes - 1 Data block securingSZ O L D0 D1 ... Dn Crc(Hi) Crc(Lo)The start code defines the frame type and is composed as follows:Bit 7 6 5 4 3 2 1 0Frame type Frame identification PLC Gateway AddressRdObj Read object 1 0 1 0 x 1 x xWrObj Write object 1 1 0 0 x 1 x xRsp Answer 0 0 0 0 0 1 0 1Ack Positive command acknowledgement 0 0 0 0 0 1 1 0Nak Negative command acknowledgement 0 0 0 0 0 1 1 1Bits 7, 6, 5 and 4 of the start code form the telegram identification; Bit 2 is alwaysì1ì.Bits 3, 1 and 0 have different meanings for the request and response telegrams.The address is only necessary for RS484.-> Compax3! the address bit (Bit 0 = 1 ) shows if the start code is followed by an address (onlyfor RS485; for RS232 Bit 0 = 0)! the gateway bit (Bit 1 = 1) shows if the message is to be passed on.(Please set Bit 1 = 0, as this function is not yet available)! the PLC bit (Bit 3 = 0 ) allows access to objects in the PLC format (U16, U32,IEEE Floating Point). For information into which PLC format the objects areconverted, please refer to the object description.Compax3 ->! Bits 0 and 1 are used to identify the response! Bit 3 is always 0The maximum number of data bytes in the request telegram is 256, in the responsetelegram 253.The block securing (CRC16) is made via the CCITT table algorith for all characters.After receiving the start code, the timeout monitoring is activated in order to avoidthat Compax3 waits in vain for further codes (e.g. connection interrupted) Thetimeout period between 2 codes received is fixed to 5ms (5 times the code time at9600Baud)Request telegramsResponse telegram
