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Operating the XtraDrive Using XtraWare
4.11. Interrupts
When an event for which an interrupt has been defined occurs, program
execution is postponed while the specified interrupt service routine is
executed. This allows the XtraDrive to react to events regardless of when
they occur. Typical interrupt events include the onset of an emergency
situation or changes in user inputs or in user or system variables.
4.11.1. Interrupt Events
Interrupt events can be either:
♦ External, such as a change in an input from one value to another,
or
♦ Internal, such as a variable value meeting a given condition.
4.11.2. Multiple Interrupts
The XtraDrive provides for eight different interrupts to be specified for a
single program. Each interrupt is assigned an identifying number from 0 to
7. The identifying number also assigns priority, where:
♦ Interrupt 0 has the highest priority.
♦ Interrupt 7 has the lowest priority.
Only one interrupt can be assigned to each priority level.
If multiple interrupts occur simultaneously, the interrupt service routines
will be run, one at a time, in order of priority.
If, while an interrupt routine is being executed, a new interrupt of a higher
priority occurs, the program will exit the present interrupt service routine
and handle the higher priority interrupt service routine. Once that service
routine has been completed, the program will continue handling the lower
priority interrupt service routine. Once all the required service routines have
been executed, the program will continue at the return point specified by
the last interrupt service routine completed.
4.11.3. Interrupt Response Time
The maximum response time to the highest priority interrupt is 2 ms. Each
lower priority interrupt is handled only once all higher priority interrupt
service routines have been completed.
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XtraWare User Manual
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