Rockwell Automation 1734-IE4S POINT Guard I/O Safety Modules User Manual - Manual (Page 83)

Rockwell Automation Publication 1734-UM013J-EN-P - July 2014 83
Configure the Module in a GuardLogix Controller System Chapter 5
2. Assign the Point Operation Type.
When you choose Equivalent or Complementary, you must also assign a
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 goes to the safe state due to a ‘cycle inputs’ required condition.
However, with a 0 ms discrepancy time setting, a fault is not 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 cycled through the safe state before the
evaluated status of the inputs can return to the Active state. When in a
‘cycle inputs’ required condition, the logical state does not necessarily
match the voltage at the terminals.
Choose Description
Single Inputs are treated as single channels.
Dual-channel safety inputs can be configured as two individual single channels.
This does not affect pulse testing because it is handled on an individual channel
basis.
IMPORTANT: Use single-channel mode when you intend to use the GuardLogix
safety application instructions.
Equivalent Inputs are treated as a dual-channel pair. The channels must match within the
discrepancy time or an error is generated.
Complementary Input are treated as a dual-channel pair. They must be in opposite states within
the discrepancy time or an error is generated.
IMPORTANT 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.