ADLINK Technology PCI-8254, User Manual

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Motion Control Theory 199
PCI-8254 / PCI-8258
4.12 Host Interrupt
An interrupt is a process starting when specified event is
encountered, the device (this controller) issue hardware interrupt
signal to the operating system, the operating system enable the
driver to execute corresponding interrupt service routine. See
figure below for illustration to this flow.
Either interrupt or polling mechanism is employed to detect the
certain event. The polling mechanism consumes CPU time
repetitively and lead to CPU over utilization. The interrupt
mechanism alert the CPU of event after it is encountered. This
process consumes much less CPU time and so can reduce CPU
utilization rate. It also frees up the CPU to process other tasks for
multi tasks and effective CPU resource utilization when waiting for
interrupt signal.
Figure 4-71: Interruption flow chart
Types of interrupt events provided by this controller are described
below:
1. Axis interrupt
2. System interrupt
3. Digital input interrupt
User space
Operation system
Controller
DLL & Driver
User’s application
Interrupt signal
Event