Error Responses - GE Power Quality Meter Series Instruction Manual

7 MODBUS COMMUNICATIONS
When a PQM detects an error other than a CRC error, a response will be sent to the master. The MSbit of the
FUNCTION CODE byte will be set to 1 (i.e. the function code sent from the slave will be equal to the function
code sent from the master plus 128). The following byte will be an exception code indicating the type of error
that occurred.
Transmissions received from the master with CRC errors will be ignored by the PQM.
The slave response to an error (other than CRC error) will be:
• SLAVE ADDRESS: 1 byte
• FUNCTION CODE: 1 byte (with MSbit set to 1)
• EXCEPTION CODE: 1 byte
• CRC: 2 bytes
The PQM implements the following exception response codes.
01 - ILLEGAL FUNCTION
The function code transmitted is not one of the functions supported by the PQM.
02 - ILLEGAL DATA ADDRESS
The address referenced in the data field transmitted by the master is not an allowable address for the PQM.
03 - ILLEGAL DATA VALUE
The value referenced in the data field transmitted by the master is not within range for the selected data
address.
GE Power Management PQM Power Quality Meter
7.2 MODBUS FUNCTIONS

7.2.11 ERROR RESPONSES

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