asm game - how implement exit to OS via PORTS int

[Asman]

Hi

Background: I'm working on some public domain very simple game in asm. I want to implement exit from game to OS or back to AsmOne ( something like exit key in WHDLoad ). I want to use PORTS int to do this. My experiment fails and I think that my knowledge how do this is weak. My first attempt was

start:		lea	(oldstack,pc),a0
		move.l	a7,(a0)

intPORTS:	 movem.l	d0-d1/a0-a2,-(a7)

		; check if keyboard casue int, get key, handskae and so on
		;set wExitKeyPressed if F1 was pressed

		movem.l	(a7)+,d0-d1/a0-a2

		tst.w	wExitKeyPressed
		beq	.exit

		pea	(oldstack,pc)

.exit		rte

Any ideas or example how do this are welcome.


Regards
asman

[Don_Adan]

Originally Posted by Asman

Hi

Background: I'm working on some public domain very simple game in asm. I want to implement exit from game to OS or back to AsmOne ( something like exit key in WHDLoad ). I want to use PORTS int to do this. My experiment fails and I think that my knowledge how do this is weak. My first attempt was

start:        lea    (oldstack,pc),a0
        move.l    a7,(a0)

intPORTS:     movem.l    d0-d1/a0-a2,-(a7)

        ; check if keyboard casue int, get key, handskae and so on
        ;set wExitKeyPressed if F1 was pressed

        movem.l    (a7)+,d0-d1/a0-a2

        tst.w    wExitKeyPressed
        beq    .exit

        pea    (oldstack,pc)

.exit        rte

Any ideas or example how do this are welcome.


Regards
asman

Better try:

intPORTS: movem.l d0-d1/a0-a2,-(a7)

; check if keyboard casue int, get key, handskae and so on
;set wExitKeyPressed if F1 was pressed

movem.l (a7)+,d0-d1/a0-a2

tst.w wExitKeyPressed
beq .exit

st quitflag

.exit rte

Add check in main interrupt for quitflag value, then quit from main interrupt, remember about restore necessary hardware registers too.

[Photon]

Since you say you're working on the game I'm sure you have a condition for exiting now, so just replace "check mousepress" or whatever with "check key".

If you're stubborn about having this int, then put the setting in the int, but move the checking outside it as Adan suggested. I doubt that you'd be able to pull off a clean exit to CLI/WB directly from within an interrupt. If you plan to have this game multitasking and that's why you feel you need all the interrupts, remember to allocate resources correctly (and then you might as well do most of the game with lib calls).

[StingRay]

Originally Posted by Asman

        tst.w    wExitKeyPressed
        beq    .exit

        pea    (oldstack,pc)

.exit        rte

Any ideas or example how do this are welcome.

pea will not work here, it trashes the stackframe. Exception stackframe is:

sr.w
returnaddress.l

So if you want to quit from IRQ, do this:

move.l #YourExitRoutine,2(a7). And in "YourExitRoutine" you restore the old stack pointer. I'd recommend to use Don Adan's way though as it's much cleaner and less error prone.

[Asman]

Hi

@Don Adan, @Photon, @StingRay

Thank you for answers. I use Don Adan's way.

Regards