Fieldbus Communication • 127MODBUS FunctionsWAGO-I/O-SYSTEM 750ETHERNET TCP/IP4.2.3.7 Function Code FC11 (Get comm event counter)This function returns a status word and an event counter from the slavedevice’s communication event counter. By reading the current count beforeand after a series of messages, a master can determine whether the messageswere handled normally by the slave.Following each successful new processing, the counter counts up. Thiscounting process is not performed in the case of exception replies, pollcommands or counter inquiries.RequestByte Field name ExampleByte 0, 1 Transaction identifier 0x0000Byte 2, 3 protocol identifier 0x0000Byte 4, 5 length field 0x0002Byte 6 unit identifier 0x01 not usedByte 7 MODBUS function code 0x0BResponseThe reply contains a 2-byte status word and a 2-byte event counter. The statusword only contains zeroes.Byte Field name Example.....Byte 7 MODBUS function code 0x0BByte 8, 9 Status 0x0000Byte 10, 11 Event Count 0x0003The event counter shows that 3 (0x0003) events were counted.ExceptionByte Field name Example.....Byte 7 MODBUS function code 0x85Byte 8 Exception code 0x01 or 0x02
