Exception Responses - GE D90 Plus Communications Manual

CHAPTER 2: MODBUS COMMUNICATION

Exception responses

PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – COMMUNICATIONS GUIDE
Table 6: Master transmission packet example, function code 05h
Packet format
Slave address
Function code
Operation code - high order byte
Operation code - low order byte
Code value - high order byte
Code value - low order byte
CRC - low order byte
CRC - high order byte
Table 7: Slave response packet example, function code 05h
Packet format
Slave address
Function code
Operation code - high order byte
Operation code - low order byte
Code value - high order byte
Code value - low order byte
CRC - low order byte
CRC - high order byte
Operation errors usually occur because of illegal data in a packet. These errors result in an
exception response from the slave. The slave detecting one of these errors sends a
response packet to the master with the high order bit of the function code set to 1.
The following tables illustrate the format of the master and slave packets for an exception
response. The example shows a master device sending the unsupported function code
39h to slave device 11.
Table 8: Exception response packet example, transmission
Packet format
Slave address
Function code
CRC - low order byte
CRC - high order byte
Table 9: Exception response packet example, reception
Packet format
Slave address
Function code
Error code
CRC - low order byte
CRC - high order byte
MODBUS FUNCTION CODES
Example (hex)
11
05
00
01
FF
00
DF
6A
Example (hex)
11
05
00
01
FF
00
DF
6A
Example (hex)
11
39
CD
F2
Example (hex)
11
B9
01
93
95
7