PACSystems™ RX3i and RSTi-EP CPU Reference Manual Section 6
GFK-2222AK October 2019
Serial I/O, SNP & RTU Protocols 189
6.3.5.1.2 Invalid Address Error Response (2)
An error response with a subcode of 2 is called an invalid address error response. This
error response is sent in the following cases:
1. The Starting Point Number and Number of Points fields specify output points or
input points that are not available in the attached CPU (returned for function
codes 1, 2, 15).
2. The Starting Register Number and Number of Registers fields specify registers
that are not available in the attached CPU (returned for function codes 4, 16).
3. The Starting Analog Input Number and Analog Input Number fields specify
analog inputs that are not available in the attached CPU (returned for function
code 3).
4. The Point Number field specifies an output point not available in the attached
CPU (returned for function code 5).
5. The Register Number field specifies a register not available in the attached CPU
(returned for function code 6).
6. The Analog Input Number field specifies an analog input number not available in
the at-attached CPU (returned for function code 3).
7. The Diagnostic Code is not equal to 0, 1, or 4 (returned for function code 8).
8. The starting Byte Number and Number of Bytes fields specify a scratch pad
memory address that is not available in the attached CPU (returned for function
code 67).
6.3.5.1.3 Invalid Data Value Error Response (3)
An error response with a subcode of 3 is called an invalid data value error response. This
response is sent in the following cases:
The first byte of the Data field is not equal to 0 or 255 (FFh) or the second byte of the Data
field is not equal to 0 for the Force Single Output Request (Function Code 5) or the initiate
communication restart request (function code 8, diagnostic code 1). The two bytes of the
Data field are not both equal to 0 for the Force Listen-Only request (Function Code 8,
Diagnostic Code 4). This response is also sent when the data length specified by the
Memory Address field is longer than the data received.
6.3.5.1.4 Query Processing Failure Error Response (4)
An error response with a subcode of 4 is called a query processing failure response. This
error response is sent by a RTU device if it properly receives a query but communication
between the associated CPU and the CMM fails.
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