ADLINK Technology PCI-8254, User Manual

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Motion Control Theory 73
PCI-8254 / PCI-8258
4.1.2 Control Cycle
The controller features three control cycle for different works. They
are:
1. Servo control cycle
2. Motion control cycle
3. Host control cycle
4.1.2.1 Servo Control Cycle
The servo control cycle is the time required to complete one close
loop control. Servo control cycle of this controller can be up to
20KHz, that is 50 microsecond for each cycle. In each control
cycle, the controller finish various servo control relevant jobs
including PID compensation and filter compensation.
4.1.2.2 Motion Control Cycle
Default motion control cycle is set at 1KHz, i.e. 1 millisecond for
each cycle. Varieties of peripheral hardware components controls,
including host communication, trajectory calculation, AMC
program execution and data sampling, are finished in it.
4.1.2.3 Host Control Cycle
Default host control cycle is 0.5 KHz. That is, it takes 2 millisecond
to finish jobs in one control cycle including communications
between hosts, watch dog, kernel update, parameter management
and other non-realtime jobs.
The servo control cycle runs independently while the motion
control and host control cycle are done in the same processor. The
controller completes scheduled jobs automatically with the motion
control ones has higher priority than the host control one.