Exception Responses; Examples - ABB C1900 Installation Manual

6 EXCEPTION RESPONSES

The exception response codes sent by the slave are shown in Table 6.1. When a slave detects one of these errors, it sends a
response message to the master consisting of slave address, function code, error code and error check fields.
Exception
Response Exception Response Name
Code
01 Illegal Function
02 Illegal Data Address
03 Illegal Data Value
07 Negative Acknowledgment
08 Memory Parity Error

6.1 Examples

A read register request to read holding register address 251 of slave 01 (undefined address for slave, beyond address limit) is
shown below.
Slave
Function
Address
01 03
The response is an exception response sighting 'illegal data address'. To indicate that the response is a notification of an error, the
most significant bit of the function code is set to 1.
Slave Address
01
The message function received is not an allowable action for the C1900.
The address reference in the data field is not an allowable address for the C1900.
The value referenced in the data field is not allowable in the addressed slave location.
The function just requested cannot be performed.
Parity check indicates an error in one or more of the characters received.
Table 6.1 Exception Response Codes
Register Start Register Start
Offset High Offset Low
00 FA
Function Exception Code
83
Exception Response Definition
Number of Number of
Registers High Registers Low
00 06
02
Error Check Field (CRC-16)
E5
Error Check Field (CRC-16)
CO F1
F9
13