10 MM300 MOTOR MANAGEMENT SYSTEM – COMMUNICATIONS GUIDE
RS485 INTERFACE (MODBUS RTU) COMMUNICATIONS GUIDE
Table 8: Master/slave packet format for function code 10H
Error Responses
When a MM300 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 MM300.
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 MM300 implements the following exception response codes:
01 - ILLEGAL FUNCTION
The function code transmitted is not one of the functions supported by the MM300.
02 - ILLEGAL DATA ADDRESS
The address referenced in the data field transmitted by the master is not an allowable
address for the MM300.
03 - ILLEGAL DATA VALUE
The value referenced in the data field transmitted by the master is not within range for the
selected data address.
MASTER TRANSMISSION BYTES EXAMPLE DESCRIPTION
SLAVE ADDRESS 1 11 message for slave
17
FUNCTION CODE 1 10 store setpoints
DATA STARTING ADDRESS 2 04 5C setpoint address
04 5C
NUMBER OF SETPOINTS 2 00 02 2 setpoints = 4
bytes total
BYTE COUNT 1 04 4 bytes of data
DATA 1 2 00 02 data for setpoint
address 04 5C
DATA 2 2 01 F4 data for setpoint
address 04 5D
CRC 2 31 11 CRC error code
SLAVE RESPONSE BYTES EXAMPLE DESCRIPTION
SLAVE ADDRESS 1 11 message from
slave 17
FUNCTION CODE 1 10 store setpoints
DATA STARTING ADDRESS 2 04 5C setpoint address
04 5C
NUMBER OF SETPOINTS 2 00 02 2 setpoints
CRC 2 82 7A CRC error code