Rockwell Automation 1715-OF8I Redundant I/O System User Manual - Manual (Page 243)

Rockwell Automation Publication 1715-UM001C-EN-P - March 2014 243
Using SIL 2 Add-On Instructions with 1715 Redundant I/O Modules Chapter 7
Performing a SIL 2 Reset SIL 2 communication between a Logix controller and 1715 modules is achieved
by the sender of the data encoding additional check data into the produced tag
and the receiver of that tag by using that extra data (and time) to determine the
data received is valid.
Data can travel in either direction, that is, CLX -> 1715 and 1715 -> CLX.
Each time the data passes the checks, it is deemed valid. If the checks fail for a
period > the CRTL value assigned to the module, a SIL 2 Reset is required.
A SIL 2 Reset acknowledges that there has been a fault within the data and that
new data, if valid, must once again be used.
The following diagram shows 1715 module output behavior.
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