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ccs and interrupt priorities

 
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dave.t
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ccs and interrupt priorities
PostPosted: Fri Dec 13, 2002 10:04 am     Reply with quote

Hi all.
Could any one explain how ccs deals with interrupt priorities.
an example:
#priority ext,timer1,timer2
How does the priority system work and are there any pitfalls to watch for!
Many thanks.
Dave Teece
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This message was ported from CCS's old forum
Original Post ID: 10032
R.J.Hamlett
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Re: ccs and interrupt priorities
PostPosted: Fri Dec 13, 2002 10:38 am     Reply with quote

:=Hi all.
:=Could any one explain how ccs deals with interrupt priorities.
:=an example:
:= #priority ext,timer1,timer2
:=How does the priority system work and are there any pitfalls to watch for!
:=Many thanks.
:=Dave Teece
All it changes, is the order that the global routine, checks the possible interrupt sources. So with your example, the code will save the registers then check the 'ext' source to see if it has caused the interrupt. This has two effects. The first is that the latency to the 'ext' code will be shorter than to the other routines, and the second is that in the event of two interrupts happening together (both being triggered in the time between starting the routine, and arriving at the test), the ext interrupt will be the one that receives service, while the other will then have to wait for the ext routine to complete, the registers to be restored, and the handler exited, before then receiving service.
The obvious problem, is in the event that a relatively slow handler, which is frequently triggered, is put into a high priority location, lower priority interrupts, may never get serviced...

Best Wishes
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This message was ported from CCS's old forum
Original Post ID: 10034
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