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 178
▪ This request disables the listen-only mode (enables responses to be sent when
queries are received so that communications can be restarted).
▪ The value of the first byte of the Data field (DATA1) must be 0 or FF. Any other value
will cause an error response to be sent. The value of the second byte of the Data field
(DATA2) is always equal to 0.
▪ The normal response to an Initiate Communication Restart query is identical to the
query.
6.3.3.9 Diagnostic Force Listen-Only Mode Request
(Loopback/Maintenance code 04):
▪ An Address of 0 indicates a broadcast request. All slave stations process a broadcast
request.
▪ After receiving a Force Listen-Only mode request, the RTU device will go into the
listen-only mode, will not perform a requested function, and will not send either
normal or error responses to any queries. The listen-only mode is disabled when the
RTU device receives an Initiate Communication Restart request or when the RTU
device is powered up.
▪ Both bytes in the Data field of a Force Listen-Only Mode request are equal to 0. The
RTU device never sends a response to a Force Listen-Only Mode request.
Note: Upon power-up, the RTU device disables the listen-only mode and is enabled to continue
sending responses to queries.

Emerson PNC001-A Series Specifications

General

Brand	Emerson
Model	PNC001-A Series
Category	Controller
Language	English