Error Responses - GE MM300 Manual

CHAPTER 2: RS485 INTERFACE (MODBUS RTU)

Error Responses

MM300 MOTOR MANAGEMENT SYSTEM – COMMUNICATIONS GUIDE
The master/slave packets have the following format:
Table 2-8: Master/slave packet format for Function Code 10H
MASTER TRANSMISSION
SLAVE ADDRESS
FUNCTION CODE
DATA STARTING ADDRESS
NUMBER OF SETPOINTS
BYTE COUNT
DATA 1
DATA 2
CRC
SLAVE RESPONSE
SLAVE ADDRESS
FUNCTION CODE
DATA STARTING ADDRESS
NUMBER OF SETPOINTS
CRC
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
02 - ILLEGAL DATA ADDRESS
03 - ILLEGAL DATA VALUE
BYTES EXAMPLE
1 11
1 10
2 04 5C
2 00 02
1 04
2 00 02
2 01 F4
2 31 11
BYTES EXAMPLE
1 11
1 10
2 04 5C
2 00 02
2 82 7A
The function code transmitted is not one of the functions
supported by the MM300.
The address referenced in the data field transmitted by the
master is not an allowable address for the MM300.
The value referenced in the data field transmitted by the
master is not within range for the selected data address.
MODBUS FUNCTIONS
DESCRIPTION
message for slave 17
store setpoints
setpoint address 04
5C
2 setpoints = 4 bytes
total
4 bytes of data
data for setpoint
address 04 5C
data for setpoint
address 04 5D
CRC error code
DESCRIPTION
message from slave
17
store setpoints
setpoint address 04
5C
2 setpoints
CRC error code
2–9