Chapter 6. Serial I/O, SNP & RTU Protocols
254 PACSystems* RX7i, RX3i and RSTi-EP CPU Reference Manual GFK-2222AD
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).
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.
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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