Dear Reinhard Meyer,
In message <4cc66a67.4000...@emk-elektronik.de> you wrote:
>
> > It fails in case the timer wraps around.
> >
> > Assume 32 bit counters, start time = 0xFFFFFFF0, delay = 0x20. It
> > will compute end = 0x10, the while codition is immediately false, and
> > you don't have any delay at all, which most probably generates a
> > false error condition.
>
> I used and assumed a 64 bit counter, that will not wrap around while
> our civilization still exists...
The code is still wrong, and as a simple correct implementation exists
there is no excuse for using such incorrect code.
Please fix that!
> If get_ticks() is only 32 bits worth, both methods will misbehave
> at a 32 bit wrap over.
No.
> > start = time();
> > while ((time() - start)< delay)
> > ...
> >
> > This works much better (assuming unsigned arithmetics).
>
> True, provided the underlying timer is really 64 bits, otherwise
> this fails, too...
You are wrong. Try for example this:
--------------------- snip -------------------
#include <stdio.h>
int main(void)
{
unsigned int time = 0xFFFFFFF0;
unsigned int delay = 0x20;
unsigned int start;
start = time;
printf("start=0x%X\n", start);
while ((time - start) < delay) {
printf("time=0x%X...\n", time);
++time;
}
return 0;
}
--------------------- snip -------------------
> Best would be to assign get_ticks() to a 32 bit unsigned and use
> 32 bit vars for start and delay as well.
? But that's what I wrote?
Best regards,
Wolfgang Denk
--
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de
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- Terry Pratchett, _Making_Money_
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