DT-INTs What's legal in an INT handler?

[circuitpro]

I wanted to clarify a point just to possibly help somebody else...

Unfortunately, TOGGLE does work to change the state of a BIT variable, even though this is an incorrect use of the command! It also quite possibly clobbers some other unsuspecting variable, in this case a LONG. It would be nice if the compiler would flag it, but it doesn't so BEWARE!!

Thanks again, Michael.

[Bruce]

Hi Charles,

What I meant was -- you don't want to jump outside an interrupt handler routine - without
returning to it.

I.E. if you GOSUB outside the interrupt routine, and don't re-enter it before your return, you might
experience major problems.

DT_INTS needs to exit from DT_INTS. If you jump outside of this routine, and try to return
from the interrupt on-your-own, you're going to have a problem.

Exit from an interruppt requires a lot of regitsers to be restored.

If you jump outside of the int routine, and return on-your-own, you will for sure see a problem.

[aratti]

I.E. if you GOSUB outside the interrupt routine, and don't re-enter it before your return, you might
experience major problems.

------------ DT Interrupt handler --------
Get_Byte:

do something here

If black then gosub apples
If withe then gosub peach

@ return


apples:
do something
return

peach:
do something
return

Bruce, can you please explain better your statement? from what you said, I understand that the above example code could give problems, while I am using this type of jump out of the interrupt handler, quite often and I never experienced any problem.

Al.

[Bruce]

Hi Al,

No problem at all with your code. You GOSUB outside the int handler, and you RETURN right back to it, so this isn't a problem.

The problem is only when you GOTO (or GOSUB) to another routine, outside an interrupt handler, and you do NOT return to it where it restores saved registers, and issues a RETFIE command.

You show a DT Interrupt handler. You may not see it, but i guarantee theres a lot of code on exit from a DT interrupt routine
that's restoring system file registers.

[Charles Linquis]

I feel better now! I haven't broken any laws.

[aratti]

Bruce, tank you for the explanation.

Al.