CHAPTER 2: RS485 INTERFACE (MODBUS RTU)
MODBUS FUNCTIONS
MM200 MOTOR MANAGEMENT SYSTEM – COMMUNICATIONS GUIDE
2-7
Function Code 07H
Modbus Implementation: Read Exception Status
MM200 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 MM200 general status byte:
The master/slave packets have the following format:
Table 2-5: Function code 7 bitmask
Table 2-6: MASTER/SLAVE PACKET FORMAT FOR FUNCTION CODE 07H
DATA STARTING ADDRESS
2
04 5C
setpoint address 04
5C
DATA
2
00 02
data for setpoint
address 04 5C
CRC
2
CB B9
CRC error code
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
MASTER TRANSMISSION
BYTES
EXAMPLE
DESCRIPTION
Bit
Function
0
Alarm
1
Trip
2
Internal fault
3
Auto
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