Interrupt Problem

[tom]

kamikaze 47:
well, of course it's better to use asm in my opinion
but this also work. I try it.

[Darrel Taylor]

Kamikaze47 is right.

There is definately a problem using PAUSE in an ASM interrupt.

Pause uses 2 internal PBP variables. (R0 and R1). So if, another PBP statement that uses either R0 or R1 gets interrupted, the interrupt routine will change those values and the main program will get confused.

It's possible to have a pause in the interrupt, IF you save both of the system vars first, then restore them when the int is finished.

In that case, toms example would look like this...

R0save VAR WORD
R1save VAR WORD

asm
int_handler
    ; Save Resisters ;
    IF (CODE_SIZE <= 2)
        movwf   wsave               ; Save W Register into wsave
        swapf   STATUS,W            ; Save STATUS Register into ssave
        clrf    STATUS                  
        movwf   ssave              
        movf    PCLATH,W            ; Save PCLATH Register into psave
        movwf   psave
        movf    FSR,W               ; Save FSR Register into fsave
        movwf   fsave
    endif
endasm
    R0save = R0
    R1save = R1
    high LED
    pause 100
    low LED
    R1 = R1save
    R0 = R0save
asm
    ; Restore Resisters ;
    movf    fsave,W             ; Restore FSR Resister
    movwf   FSR                 
    movf    psave,W             ; Restore PCLATH Resister
    movwf   PCLATH
    swapf   ssave,W             ; Restore STATUS Resister
    movwf   STATUS
    swapf   wsave,F             ; Restore W Resister
    swapf   wsave,W
    bcf INTCON,1
    retfie
endasm

But then, like tom says ... "it is not advisable to use delays in interrupt"
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[Kamikaze47]

Thanks for that info Darrel.

Is there a reference somewhere that tells you what (if any) internal variables PBP uses for each command?

[Darrel Taylor]

No, unfortunately.

Depending on how and where certain statements are used in the program, the actual system variables used might change. So there's really no way to make a "List".

You pretty much have to sift thru the .LST file to find out which vars are used. That includes following every CALL to other routines too. It can take a while.

PAUSE was easy though, it's pretty small, and only has 1 CALL.

Of course, you can take the easy route and just save them all to be sure. But then we're back to OXIMBIT's routine again.
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[rhino]

Kamikaze47 -
There's a little info about this HERE from Darrel. Look at post #9 on down. I guess it's out there if you have the time to dig through the files and look for them.