Exception response packet
- Last UpdatedNov 18, 2022
- 1 minute read
If a Modbus device responds to a request with an exception response, a value of 0x80 will be added to the function code with a logical OR operation to form the error code in the response packet. It will be followed by one of the exception codes that represent the reason for the error in the next byte of the packet. For example, if a read holding request (function code 0x03) fails the response will contain 0x83 for the error code.
The format of an exception response packet is shown below:
|
PLC Node Address |
1 Byte |
1 to 255 |
|---|---|---|
|
Error Code |
1 Byte |
0x83 |
|
Exception Code |
1 Byte |
01 or 02 or 03 or 04 |