counting time...16F876

[digitalfreak]

I have an issue of counting. I have to run a while loop for some 10 seconds OR until gets signal. I think I cannot use delay here. Is there any better way other than using a counter and count instructions to know the time.

the loop is very simple and looks something like following...

[Ttelmah]

First comment. You don't need to keep setting the PWM duty to 50. It stays where it is set.
Second comment. Three instructions per loop!.... You probably have something like 20 instructions in the loop. You are testing a 16 bit value, which implies fetching two bytes, and comparing these against the constant. Probably about six to eight machine instructions. The input test will take a couple of instructions. The loop itself, involves a couple of machine cycles. Setting the PWM duty, should only involve two instructions (since your value is a 'short', the code just needs to load the constant value, then load this into the PWM register). The ouput instruction then probably adds only one instruction.
The 'best' way, is probably to use one of the hardware timers, (assuming your chip has these). Alternatively, use the RTCC (this is a hardware timer too, but one all the pics have, which in it's default setup, basically counts instructions, from 0 to 255 - you can test for it's interrupt flag becoming set, and clear this,and _know_ that 256 instruction times have passed since the last time this happened - except on the larger PICs which can be set to have this count up to 65536). This then gives you a counter that is independant of the code.

Best Wishes

[digitalfreak]

thx 4 ur time. I will try to work on it and post.