Emerson PNC001-A Series User Manual

PACSystems™ RX3i and RSTi-EP CPU Reference Manual Section 6
GFK-2222AK October 2019
Serial I/O, SNP & RTU Protocols 177
6.3.3.7 Message (08): Loopback/Maintenance (General)
6.3.3.7.1 Format:
Figure 30: RTU Loopback/Maintenance Message Format
Address
Diagnostic
c
Code
Data
Error Check
Func
08
Query
0, 1, or 4
DATA 1
DATA 1
Address
Diagnostic
c
Code
Data
Error Check
Func
08
Normal Response
0, 1, or 4
DATA 1
DATA 1
6.3.3.7.2 Query:
▪ The Function code is equal to 8.
▪ The Diagnostic Code is two bytes in length. The high order byte of the Diagnostic
Code is the first byte sent in the Diagnostic Code field. The low order byte is the
second byte sent. The loopback/maintenance command is defined only for
Diagnostic Codes equal to 0, 1, or 4. All other Diagnostic Codes are reserved.
▪ The Data field is two bytes in length. The contents of the two Data bytes are defined
by the value of the Diagnostic Code.Response:
▪ See descriptions for individual Diagnostic Codes.
▪ Diagnostic Return Query Data Request (Loopback/Maintenance Code 00):
▪ An address of 0 is not allowed for the return query data request.
▪ The values of the two Data field bytes in the query are arbitrary.
▪ The normal response is identical to the query.
▪ The values of the Data bytes in the response are equal to the values sent in the query.
6.3.3.8 Diagnostic Initiate Communication Restart Request
(Loopback/Maintenance Code 01):
▪ An Address of 0 indicates a broadcast request. All slave stations process a broadcast
request and no response is sent.

Emerson PNC001-A Series Specifications

General

Brand	Emerson
Model	PNC001-A Series
Category	Controller
Language	English