HEIDENHAIN iTNC 530 HSCI Technical Manual page 1666

1666
In most cases a "double" loop in the (S)PLC program can be used to prevent
the triggering of such reactions, for example with low test pulses with a pulse
width greater than 2.0 ms. This filters the test pulses with the goal of further
processing only static signals that are available at the (S)PLC input for more
than two (S)PLC cycles.
Example of such a loop for filtering during use of a guard-door switch with test
pulses:
;Filter I_GuardDoorSwitch_closed by one PLC cycle
;
L I_Workspace_to_sensor
A ML_Workspace_was_closed
S I_Workspace_closed
program
LN I_Workspace_to_sensor
AN ML_Workspace_was_closed
R I_Workspace_closed
L I_Workspace_to_sensor
= ML_Workspace_was_closed
Note
Remember the following when using such a loop:
The information on the status of such filtered signals is processed by the

loop with a delay of one (S)PLC cycle. This has to be considered in the
control's reaction times.
It must be possible to rule out a synchronization between the (S)PLC

program and the test pulse. Otherwise a test pulse beyond several
(S)PLC cycles might be detected and therefore not be filtered out.
The repetition rate or the cycle of the test pulse must be greater than
twice the (S)PLC cycle time for this purpose.
(e.g. a repetition rate of > 2 x 21 ms)
Test the (S)PLC program on the machine.

Module 9196 Find the PLC cycle time
The PLC cycle time is determined in µs.
Call:
CM 9196
PL D <>PLC cycle time in µs>
MP7602 PLC cycle time
Input: 0 to 60 ms
0 to 12 = 12 ms
Note
An exact PLC cycle time is only available after the emergency stop test.
;Sensor signal is pulsed
;modified signal, used in the PLC
HEIDENHAIN Technical Manual iTNC 530 HSCI