Re: A92: 256K & interrupt routines
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Re: A92: 256K & interrupt routines
Jean-Jacques MICHEL wrote:
>
> I have just upgraded my TI92 to 256K (No need to ask me how, this is not the question !)
>
> I also made a small patch in order to have Fargo run with this upgrade
> (Once more, this is not the reason for my question !)
>
> I noticed that some programs were not running, and looking at the SPRITE example,
> I suspect that this problem is related to the way interruption re-routing is done
> in some programs.
>
> Could somebody justify the use of :
>
> move.w #$2700,sr
> move.l ($020064),old_int_1
> move.l #int_1,($020064)
> move.w #$2000,sr
>
> instead of
>
> move.w #$2700,sr
> move.l ($64),old_int_1
> move.l #int_1,($64)
> move.w #$2000,sr
>
> to save and re-route interrupt $64 ????
>
> Because with 128K more, $20064 is a RAM position, not the $64 interrupt vector !!!
>
> JJM
It saved you the trouble of setting/clearing the bit that
enables/disabled the "unauthorized writing under $120" trap.
It's the same technique used by Fargo itself - the memory wraps around
at $020000, and the trap isn't activated "up there".
References: