Single and Dual Data Highway Configurations
Publication PUB088-005-00_1017
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4.4.1
Extended Diagnostic Messages for RedCom
The Redundancy Extensions to the standard V1 protocol allow the two channels to communicate
between themselves to establish correct operation of the highway if there is a failure, both the Simple
and RedCom versions of the card do this. In addition to these, there are extra Extended Diagnostic
messages that are reported to the PLC as part of the RedCom system that the Dual RedCom card
reports. Not all PLCs are RedCom compliant, so some are unable to understand these messages and,
as a consequence, will mark the device as having an Error. If this is the case, either reconfigure the
Profibus card to be ‘Simple’ or disable the PLC’s diagnostics package that is looking at the extended
diagnostics.
A RedCom Dual Channel card can be altered to a Simple Dual Channel card, or vice versa, by
entering the appropriate value in parameter 15 in the GSD file.
The extended diagnostics is contained in 3 bytes in the diagnostic message and is reported by the
Primary slave only:
Description
Comment
Headerbyte
= 8 hex
Status_Type
= 9Fhex
Slot_Number
= 0 hex
Specifier
Function
Red_State_1
State of Primary slave
Red_State_2
State of Back Up slave
Red_State_3
Not used
The information in the Red_State bytes is as below
Bit No:
7
6
5
4
3
2
1
0
Description if set:
This slave is the Back up
This slave is the Primary
There is a Hardware defect
This slave is in Data Exchange mode
Master State Clear
Baud rate found
Toh started (hold timer active – set if a change
of channel is imminent
Reserved
