A synchronous I/O task that runs as a routine of the scheduler process (sched). It always executes at the beginning of the input stage of the test cycle in parallel with the other synchronous tasks. It updates item values into the RTDB on behalf of asynchronous tasks and HMI operator entry.
Since changes in RTDB values can only occur when neither the Script no the models are using values in the RTDB, asynchronous processes cannot write values into the RTDB directly. The asynchronous processes place requests for data value updates by putting them into a shared FIFO queue that is processed by this I/O task.
This task polls the sync input FIFO queue for a limited duration. Any requests placed into the FIFO before that duration expires will be processed. The default limit is 20 microseconds, but a different value can be specified when creating a test session.
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