Technical data

224 • Fieldbus Communication
MODBUS Functions
WAGO-I/O-SYSTEM 750
BACnet/IP Controller
4.3.3.7 Function Code FC11 (Get comm event counter)
This function returns a status word and an event counter from the slave de-
vice’s communication event counter. By reading the current count before and
after a series of messages, a master can determine whether the messages were
handled normally by the slave.
Following each successful new processing, the counter counts up. This count-
ing process is not performed in the case of exception replies, poll commands
or counter inquiries.
Request
Byte Field name Example
Byte 0, 1 Transaction identifier 0x0000
Byte 2, 3 protocol identifier 0x0000
Byte 4, 5 length field 0x0002
Byte 6 unit identifier 0x01 not used
Byte 7 MODBUS function code 0x0B
Response
The reply contains a 2-byte status word and a 2-byte event counter. The status
word only contains zeroes.
Byte Field name Example
.....
Byte 7 MODBUS function code 0x0B
Byte 8, 9 Status 0x0000
Byte 10, 11 Event Count 0x0003
The event counter shows that 3 (0x0003) events were counted.
Exception
Byte Field name Example
.....
Byte 7 MODBUS function code 0x85
Byte 8 Exception code 0x01 or 0x02