beginer help needed

[asifiqbal]

thankyou sir ur reply was helpful, i have another question to ask, my device is pic 16f72 and port b is digital
when a programm run in a loop how can i intrrupt it for example
main:
high portb.7
pause 100
low portb.7
pause 100
goto main
------
now this loop keep repeating how can i intrrupt this loop ? if i write like this
main:
high portb.7
pause 100
low portb.7
pause 100
goto main
if portb.2=0 then
portb.7 = 0
endif
------------
intrrupt here doesnt work what is the way out to get out of the loop now

[Dave]

main:
high portb.7
pause 100
low portb.7
pause 100
if portb.2=0 then goto EXIT 'test for exit 1 time for each loop
goto main
EXIT:
portb.7 = 0
remaining code goes here...........


OR
main:
high portb.7
if portb.2=0 then goto EXIT 'test for exit after setting port pin high
pause 100
low portb.7
if portb.2=0 then goto EXIT 'test for exit after setting port pin low
pause 100
goto main
EXIT:
portb.7 = 0
remaining code goes here...........

[HenrikOlsson]

Hi,
There are several ways of doing it.
One way is to actually use a hardware interrupt, another way is to simply poll the input periodically as you go thru the loop. Yet another way is to move away from the loop structure and use a state machine aproach instead. Instead of using PAUSE, which "blocks" the processor, you can use hardware timers, either with interrupts or by simply polling the interrupt flag. It really depends on what you want to do and how fast you need to do it.

If all you want to do is blink the LED untill an input goes high (or low) then you basically had it in the first example you posted. The drawback there is that the input is only checked once per iteration thru the loop so if the PAUSE is long there will be a long "reaction time".

As you see there's not a single answer to your question, it all depends....