Multilin SR469, Instruction Manual

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ERROR RESPONSES 6. COMMUNICATIONS
6-14
6.4 ERROR RESPONSES
6.4.1 ERROR RESPONSES
When an SR469 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 SR469.
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 SR469 implements the following exception response codes.
01 - ILLEGAL FUNCTION
The function code transmitted is not one of the functions supported by the SR469.
02 - ILLEGAL DATA ADDRESS
The address referenced in the data field transmitted by the master is not an allowable address for the SR469.
03 - ILLEGAL DATA VALUE
The value referenced in the data field transmitted by the master is not within range for the selected data address.