Exception Codes

There are scenarios where the PLC can issue invalid queries to the IS4310 (Modbus Slave). In such cases, the IS4310 will respond to the PLC (Modbus Master) with one of the following Modbus Exception Codes:

Code 1: ILLEGAL FUNCTION

The Modbus Master queried a non-valid Function Code to the IS4310 (Modbus Slave). Valid Function codes are 0x03, 0x06, 0x10.

Code 2: ILLEGAL DATA ADDRESS

The Modbus Master attempted to read or write one or more Holding Registers higher than 503.

Alternatively, the query's starting register was valid, but the total number of registers requested exceeded 503.

Code 3: ILLEGAL DATA VALUE

The query performed by the PLC has errors.