Disabling interrupts

[exxos]

Can anyone shed any light on this code which disables interrupts. Really I want to know if this works fine for TOS104 and TOS206 on a 68000 CPU.

Code: Select all

sys_sleep:
	lea		sys_state(pc),a0
	ori.w		#$0700,sr
	move.l		$70.w,(a0)+
	move.l		$114.w,(a0)+
	lea		new_vbi(pc),a1
	move.l		a1,$70.w
	lea		new_tc(pc),a1
	move.l		a1,timerc.w
	andi.w		#$f3ff,sr
	rts

[thorsten.otto]

Its cleaner to save the old value of SR, and restore it at the end, rather than just doing andi $f3ff,sr. Depending on where you call your code, interrupts might have already been disabled before, or the mask being set to a different value than 3, and then you would unintentionally enabling them.

Other than that, it looks ok to me.

[exxos]

Its cleaner to save the old value of SR, and restore it at the end, rather than just doing andi $f3ff,sr. Depending on where you call your code, interrupts might have already been disabled before, or the mask being set to a different value than 3, and then you would unintentionally enabling them.

Other than that, it looks ok to me.

Cool thanks.

I never thought calling the code twice could enable them again..

[exxos]

Its cleaner to save the old value of SR, and restore it at the end, rather than just doing andi $f3ff,sr. Depending on where you call your code, interrupts might have already been disabled before, or the mask being set to a different value than 3, and then you would unintentionally enabling them.

Can you explain how to enable and disable the interrupts like that code does ? When I poke in STOS I get back $E03662.. I have no idea what that number is for or what bits to change ?

[thorsten.otto]

Code: Select all

sys_sleep:
	lea		sys_state(pc),a0
	move.w          sr,d0   <-- save old value
	ori.w		#$0700,sr
	move.l		$70.w,(a0)+
	move.l		$114.w,(a0)+
	lea		new_vbi(pc),a1
	move.l		a1,$70.w
	lea		new_tc(pc),a1
	move.l		a1,timerc.w
	move.w		d0,sr   <-- restore old interrupt mask
	rts

That's all i suggested to change.

[exxos]

That's all i suggested to change.

Yeah, though I didn't program that ASM code, so no idea what its really doing. I need to be able to do this in HISOFT BASIC.

[thorsten.otto]

I don't know hisoft basic, but i would be surprised if you have access to the SR register there. And the interrupt routines that are installed there must be written in asm, anyway, since they must return with rte, and must not change any registers.