CHAPTER 8: MODBUS FUNCTIONS ERROR RESPONSES
SR3 SERIES PROTECTIVE RELAY PLATFORM – COMMUNICATIONS GUIDE 8-15
Response:
Error Responses
When a 3 Series relay 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 3 Series
relay.
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 3 Series relay implements the following exception response codes:
01 - ILLEGAL FUNCTION
The function code transmitted is not one of the functions supported by the 3 Series
relay.
02 - ILLEGAL DATA ADDRESS
The address referenced in the data field transmitted by the master is not an allowable
address for the 3 Series relay.
03 - ILLEGAL DATA VALUE
The value referenced in the data field transmitted by the master is not within range for
the selected data address.
Byte Count 04 02
Data Hi 00
Data Lo 01
Field Name Hex
Slave Address FE
Function 43
Starting Address Hi 09
Starting Address Lo C1
No. of Registers Hi 00
No. of Registers Lo 01
Field Name Hex
To Next Page
Loading...
Need help?
General
