Rockwell Automation 1791DS-IBxxxx Guard I/O DeviceNet Safety Modules - Manual (Page 87)

Rockwell Automation Publication 1791DS-UM001J-EN-P - May 2013 87
Configure Modules in RSNetWorx for DeviceNet Software Chapter 6
2. Assign the Operation Type.
When you choose Equivalent or Complementary, you must also assign an
appropriate operation discrepancy time.
A discrepancy time setting of 0 ms means that the channels in a dual
configuration can be discrepant for an infinite amount of time without a
fault being declared.
For a discrepancy time setting of 0 ms, the evaluated status of the inputs
still go to the safe state in the event of a ‘cycle inputs’ required condition.
But, due to the 0 ms discrepancy time, a fault will not be declared.
A ‘cycle inputs’ required condition occurs when one input terminal goes
from its normal active>inactive>active state while the other input terminal
remains in its normal active state. Even though no fault is declared, the
inputs must be cycles before the evaluated status of the inputs can return to
the active state.
Choose Description
Single Inputs are treated as single channels. In many cases, dual-channel safety inputs
are configured as two individual, single channels. This does not affect pulse testing
because it is handled on an individual basis.
Equivalent (1) Inputs are treated as a dual-channel pair. The channels must match within the
discrepancy time or an error is generated.
Complementary (1) Inputs are treated as a dual-channel pair. They must be in opposite states within
the discrepancy time or an error is generated.
(1) Be aware that configuring discrepancy time on safety I/O modules masks input discrepancies detected by the controller
safety instructions. Status can be read by the controller to obtain this fault information.