interrupt delay

[bear]

how to interrupt during delay??

[aurora]

Which interrupt?

If you have enable interrupt(s), your program(in main) will automatically enter interrupt mode when it detect change(s). After complete the interrupt routine, it will return to where it left.

[bear]

i want to interupt the programe during its doing delay(delay function)..

[yonghui]

hi,

the interrupt wont be blocked by any routine in the main program. it will just jump out of it by pushing any necessary data to the stack and go into interrupt vector then execute the interrupt routine and jump back and pop off the stack the data and continue the routine in main program.

delay wont block the interrupt from happening

[ABSF]

That means C doesnt use any of the timers to do its delay function?

Allen

[zhenning]

Allen, you can use timer to do the delay. I think, bear is afraid that the interrupt wont work during delay. Actually interrupt can work anytime it needs to as long as it is triggered

[ABSF]

What I meant is C doesn't implement delay functions using timer interrupt?

There must be a clock tick of 1mS or 10mS somewhere in C so the delay function would be accurate. In other words, how does the delay function in C works?

Allen

[ABSF]

I just found out that the delay functions in HiTech C works by wasting time in delay loops. So interrupt shouldn't have any conflict with it.

Thanks.

Allen

[shahrul]

Sometimes I prefer timer interrupt to do delay, manual looping delay wasting program processing.

[aurora]

Delay functions by counting the clock cycle to meet the duration specified. For example, calling delay of 1ms on a 10Mhz circuit, the compiler will calculate the number of clock cycle that it need to track. (In this case, 2500 clock cycle = 1ms).

You won't see this, but when it compile, it will write something like

CODE: SELECT_ALL_CODE

while(counter <= 2500)
{ do nothing
}

before jumping to the line.

So when you have an interrupt:
1. uC will stop the delay function (hence stop the counter)
2. Begin interrupt routine
3. Finish interrupt routine
4. Resume delay function (resume counter)

The problem with the above, the delay function ignore all the clock cycle which happen during interrupt. If your interrupt take 200uS, the delay function actually prolong to 1.2ms (instead of 1ms).

To overcome this, some people prefer to use timer interrupt. Because timer interrupt function exactly like above, but better as it also continue to count the counter.

Or, write your own delay function:

CODE: SELECT_ALL_CODE

while(counter <= 2500)
{ do something here
}

Well, people don't usually do this, unless there is something more important, like another even higher priority interrupt.