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Relay control (like voting logic) is implemented by the main module
instructing the auxiliary module on how to set its relay outputs in any
particular circumstance. However, to guard against the situation where a main
module or link failure prevents proper instruction from reaching it, on
detecting a communication link failure the auxiliary module sets any fail-safe
relays to their alarm state (de-energized). This function is an automatic/
autonomous action by the auxiliary module.
Table 250 - Relay Source Decoding
Bit
Description
0
OFF
1...13
Voted Alarm Instance 1...13
Output Type: Alert
14...16
Reserved
17...29
Voted Alarm Instance 1...13
Output Type: Danger
30...32
Reserved
33...45
Voted Alarm Instance 1...13
Output type: TX OK
Higher Values
Reserved
126
Dedicated, Bypass Active Relay
127
Dedicated, Fault Relay, Relay Control Determines Faults
As the special functions (126 and 127) are not the result of Voted alarms, there
is no definition of type - suggest fail-safe is adopted for these. Local Relay
Control also includes a Latching bit, to give a latching control to these special
functions.
0x00 defines the relay as disabled, multiple sources not allowed.
Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
CIP Objects
Appendix A
501
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