Rockwell Automation Publication 2080-UM002L-EN-E - November 2021
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Chapter 8 Use the High-Speed Counter and Programmable Limit Switch
Figure 12 - PLS Data Block
PLS Operation
When the PLS function is enabled, and the controller is in the run mode, the
HSC counts incoming pulses. When the count reaches the first preset (HSCHP
or HSCLP) defined in the PLS data, the output source data (HSCHPOutput or
HSCLPOutput) is written through the HSC mask (HSCAPP.OutputMask).
At that point, the next presets (HSCHP and HSCLP) defined in the PLS data
become active.
When the HSC counts to that new preset, the new output data is written
through the HSC mask. This process continues until the last element within
the PLS data block is loaded. At that point, the active element within the PLS
data block is reset to zero. This behavior is referred to as circular operation.
If invalid data is loaded during operation, an HSC error is generated and
causes a controller fault.
You can use the PLS in Up (high), Down (low), or both directions. If your
application only counts in one direction, ignore the other parameters.
The PLS function can operate with all of the other HSC capabilities. The ability
to select which HSC events generate a user interrupt are not limited.
The HSCHPOutput is only written when HSCHP is reached. The
HSCLPOutput is written when HSCLP is reached.
Output High Data is only operational when the counter is counting up.
Output Low Data is only operational when the counter is counting down.
