Rockwell Automation Publication 1791ES-UM001G-EN-P - November 2016
17
Safety Function Operation
Chapter 1
Set Dual-channel Mode and Discrepancy Time
To support redundant channel safety devices, the consistency between signals
on two channels can be evaluated. Either equivalent or complementary can be
selected. This function monitors the time during which there is a discrepancy
between the two channels.
If the length of the discrepancy exceeds the configured discrepancy time, the
safety input data and the individual-safety input status turn off for both
channels. The configured discrepancy time is 0…65,530 ms in increments of
10 ms.
shows the relation between input terminal states and controller input
data and status.
Dual-channels, Equivalent
In Equivalent mode, both inputs of a pair must typically be in the same
(equivalent) state. When a transition occurs in one channel of the pair, before
the transition of the second channel of the pair, a discrepancy occurs. If the
second channel transitions to the appropriate state before the discrepancy time
elapses, the inputs are considered equivalent. If the second transition does not
IMPORTANT
The dual-channel function is used with two consecutive inputs that are
paired together, this process starts at an even input number, such as
inputs 0 and 1; 2 and 3; and so on.
IMPORTANT
Do not set the discrepancy time longer than necessary. The purpose of
the discrepancy time is to allow for normal differences between contact
switching when demands are placed on safety inputs. For this testing to
operate correctly, only one demand on the safety input is expected
during the discrepancy time. If the discrepancy time is set too high, and
multiple demands occur during this time, then both safety input
channels will fault.
Table 2 - Terminal Input Status and Controller I/O Data
Dual-channel Mode
Input Terminal
Controller Input Data and Status
Dual- channel
Resultant
Data
Dual-channel
Resultant
Status
IN0
IN1
Safety
Input 0 Data
Safety
Input 1 Data
Safety
Input 0 Status
Safety
Input 1 Status
Dual-channels, Equivalent
OFF
OFF
OFF
OFF
ON
ON
OFF
Normal
OFF
ON
OFF
OFF
OFF
OFF
OFF
Fault
ON
OFF
OFF
OFF
OFF
OFF
OFF
Fault
ON
ON
ON
ON
ON
ON
ON
Normal
Dual-channels, Complementary OFF
OFF
OFF
ON
OFF
OFF
OFF
Fault
OFF
ON
OFF
ON
ON
ON
OFF
Normal
ON
OFF
ON
OFF
ON
ON
ON
Normal
ON
ON
OFF
ON
OFF
OFF
OFF
Fault
Summary of Contents for 1732ES-IB12XOB4
Page 6: ...6 Rockwell Automation Publication 1791ES UM001G EN P November 2016 Table of Contents Notes ...
Page 8: ...8 Rockwell Automation Publication 1791ES UM001G EN P November 2016 Summary of Changes Notes ...
Page 174: ...174 Rockwell Automation Publication 1791ES UM001G EN P November 2016 Index Notes ...
Page 175: ......