Rockwell Automation 1791DS-IBxxxx Guard I/O DeviceNet Safety Modules - Manual (Page 33)

Rockwell Automation Publication 1791DS-UM001J-EN-P - May 2013 33
Understand the Operation of Safety Functions Chapter 2
Safety Input Fault Recovery
If an error is detected, the safety input data remains in the off state. Follow this
procedure to activate the safety input data again.
1. Remove the cause of the error.
2. Place the safety input (or safety inputs) into the safe state.
The safety input status turns on (fault cleared) after the input-error latch
time has elapsed and the I/O indicator (red) turns off. The input data can
now be controlled.
Input Delays
On-delay - An input signal is treated as Logic 0 during the on-delay time (0…126
ms, in increments of 6 ms) after the input contact’s rising edge. The input turns
on only if the input contact remains on after the on-delay time has elapsed. This
helps prevent rapid changes of the input data due to contact bounce.
Figure 17 - On-delay
Off-delay - An input signal is treated as Logic 1 during the off-delay time (0…126
ms, in increments of 6 ms) after the input contact’s falling edge. The input turns
off only if the input contact remains off after the off delay time has elapsed. This
helps prevent rapid changes of the input data due to contact bounce.
Figure 18 - Off-delay
ON
OFF
ON
OFF
Remote I/O
Data Safety
Input
Input Signal
ON-delay
44094
On-delay
Input Signal
ON
OFF
ON
OFF Remote I/O Data
Safety Input
OFF
ON
OFF Safety Input
Input Signal
OFF-delay
44095
Remote I/O Data
Safety Input
Input Signal
ON
OFF
ON
OFF
Off-delay