Siemens SIMATIC S7-1500 Manual page 29

PP operation
The M-switch is meaningless during the light test in PP operation. The light test corresponds
to the switch-on test and current flows through the load. The light test is always activated in
PP operation.
①
Image 4-7
If the readback signals are incorrect, the signal is present for the configured readback time at
the output channel before the fault causes passivation of the output channel.
If the signal was not read back correctly once the maximum readback time switch on test has
expired, the output channel is passivated.
No new process values are switched to the output channels while a bit pattern is still active
(switch test is carried out). This means that a higher maximum readback time switch on test
for the light test increases the response time of the F-module.
Test pulses of the light test
*
Image 4-8
Digital output module F-DQ 8x24VDC/2A PPM (6ES7526-2BF00-0AB0)
Manual, 01/2016, A5E03858037-AA
Readback
Functional principle of the light test (PP switching)
Output of test pulses only during test cycle. The module cycle is 5 ms.
Test pulses of the light test
Parameters/address space
4.2 Explanation of parameters
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