8MM300 MOTOR MANAGEMENT SYSTEM – COMMUNICATIONS GUIDE
RS485 INTERFACE (MODBUS RTU) COMMUNICATIONS GUIDE
Function Code 07H
Modbus Implementation: Read Exception Status
MM300 Implementation: Read Device Status
This is a function used to quickly read the status of a selected device. A short message
length allows for rapid reading of status. The status byte returned will have individual bits
set to 1 or 0 depending on the status of the slave device. For this example, consider the
following MM300 general status byte:
The master/slave packets have the following format:
Table 5: Function code 7 bitmask
Table 6: Master/slave packet format for function code 07H
SLAVE RESPONSE BYTES EXAMPLE DESCRIPTION
SLAVE ADDRESS 1 11 message from
slave 17
FUNCTION CODE 1 06 store single
setpoint
DATA STARTING ADDRESS 2 04 5C setpoint address
04 5C
DATA 2 00 02 data stored in
setpoint address
04 5C
CRC 2 CB B9 CRC error code
Bit Function
0Alarm
1Trip
2 Internal fault
3Auto
4 Contactor A
5 Contactor B
6 Contact output 3
7 Drive available (communications control)
MASTER TRANSMISSION BYTES EXAMPLE DESCRIPTION
SLAVE ADDRESS 1 11 message for slave
17
FUNCTION CODE 1 07 read device status
CRC 2 4C 22 CRC error code
SLAVE RESPONSE BYTES EXAMPLE DESCRIPTION
SLAVE ADDRESS 1 11 message from
slave 17
FUNCTION CODE 1 07 read device status
DEVICE STATUS (see
definition above)
1 2C status = 00101100
(in binary)
CRC 2 22 28 CRC error code