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User Actions Scheduler

The UAS function block allows an application software to postpone the execution of the actions.

Scheduler Reference Settings

Prior to using the User Actions Scheduler, the user application has to select a 32-bit reference counter. This is achieved by assigning one of the following three values to the UserActionsSchedulerReference GenICam feature:

  • InternalTime selects the Coaxlink card local time: A monotonic time base that increments by 1 every 1 microsecond and wraps around after about 71 minutes when it reaches the maximum value of 4,294,967,295.
  • QDC1Position and QDC2Position selects the Position Counter of the Quadrature Decoder tools QDC1 and QDC2 respectively.

Important: For correct operation of the UAS with a position reference, both conditions must be satisfied:

  • The position counter must increment monotonically!
  • The position counter may not increment faster than every microsecond.

Note: To ensure monotonic increments of the QDC position counter:

  • Set properly QuadratureDecoderToolForwardDirection such that the counter increments when the object moves in the forward direction.
  • If it exists any backward motion, prevent the position counter to decrement by setting the QuadratureDecoderToolOutputMode to ForwardOnly or to FirstPassForwardOnly.

Schedule User Actions Pool Operation

The Scheduled User Actions Pool is a memory area where the Scheduled User Actions Sets are stored by the user application. The pool has 64 locations.

To add a new Scheduled User Actions to the Pool, the user application must:

  1. Ensure that there is at least one free location by getting the value of the ScheduledUserActionsPoolStatus GenICam feature,
  2. Define a User Actions Set,
  3. Determines the time/position 32-bit value when the actions are to be executed,
  4. Set this value to ScheduledUserActions GenICam feature.

Scheduled User Actions are removed from the pool when they are executed.

The pool can be cleared at any time by executing the DiscardScheduledUserActions GenICam command.

Scanner Operation and Scheduled Actions Execution

At every increment of the 32-bit (time or position) reference counter, the Scanner reads all the locations and compares the scheduled reference time/position with the current time/position count value.

When the values are identical, the Scheduled User Actions Set is elected for execution at the end of the scan and removed from the pool.

When multiple sets are elected for execution, their actions are merged.

Note: Merging a set low and a set high action on the same User Output Register bit results into a toggle action.

At the end of the scan: the merged elected actions are executed simultaneously. The time delay from the reference tick up to the execution of the elected actions is very small ( sub-microsecond) and constant.