AVR-Chat

>> So I have this Mega32 running at 4 MHz (yes, 4 MHz, I checked the fuses)
>>
>> I'm trying to measure two pulse widths, on INT0 and INT1 using T1 with
>> a divisor of 1.
>> The pulses have a minimum period of 5uS, nominal period of 14uS, and
>> max of 23uS.
>> I can't adjust those values.
>>
>> I enable INT0 for a rising edge int.
>> When the int happens, I zero T1, and exit the ISR.
>> When the int happens again, I read T1 and store it.
>>
>> Then I disable INT0, enable INT1, and do the same thing for the pulse
>> on that input.
>>
>>
>> My problem is that the system seems to be running much slower than I
>> would expect.
>> The interrupt latency is measuring out more than 5uS!
>>
>> I don't have any other ints enabled, other than a very simple T0 ISR
>> (see previous post)
>>
>> There's no point where I have ints disabled, at least not in the code
>> that I wrote.
>>
>> Do I really have to run the machine faster than this?
>> I wouldn't expect to have to in Asm..
>>
>>
>>
>>
>> --
>>
>> "The very powerful and the very stupid have one thing in common. Instead
>> of
>> altering their views to fit the facts, they alter the facts to fit their
>> views... which can be very uncomfortable if you happen to be one of the
>> facts that needs altering." Doctor Who, Face of Evil
>>
>
> Well, interrupts are disabled inside ISRs!
>
> Jim Wagner
>
>
>
>

There is a current thread on AVRFreaks that sounds VERY similar to your
problems: Interrupt problem (timer1 timing + 'interference')

http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=75366

Jim