Dear Reinhard Meyer,
In message 4CC66A67.4000608@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