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The high-accuracy PLS timing mode is activated by HWAssistance.

  • PLS High Accuracy On (<pls>.HWAssistance = 1)
When high-accuracy mode is active, the Product software extrapolates the exact time at which the axis will reach the PLS position, based on its current position, velocity and acceleration, and sets an output event for that time.
If HWAssistance is active, the timing of the PLS output switch will be computed to an accuracy of microseconds.
The exact timing of the PLS switch is computed according to the current velocity and acceleration values of the samples before and after the PLS position.
In instances of constant acceleration or linear acceleration change between the two samples, the timing of the PLS is computed exactly to ±1µs.
  • PLS High Accuracy Off (<pls>.HWAssistance = 0)
When HWAssistance is not active (normal PLS), the PLS outputs are toggled at the moment the PLS source crosses the PLS position.
The timing of the PLS switch is always an integer number of motion samples; therefore, the ::timing accuracy of the PLS is equivalent to the motion bus cycle.
Note that with fw version 4.5.29 and before, the position command delay of PositionErrorDelay-2
samples will be taken into account as hard-coded expression. This means that in case of PositionErrorDelay = 3,
when the PLSposition is passed, the output will be triggered after 1 sample delay plus Δt, the inter-sample delay.
Hwassistance is available only in systems that have the hardware that support this functionality

Short form



?<pls>. HWAssistance


Versions 4.4.5 and higher




1 - TRUE  - starts the hardware assisted PLS  mode





Configuration, Task or Terminal


  • Available only in systems with hardware that supports this functionality (MIB)
  • Modal/Nodal
  • High-accuracy PLS timing mode works only on system digital ouputs (System.Dout) 1 to 8


?PLS1. HWAssistance

PLS1. HWAssistance = True

See Also