[A83] Re: rst 20h crap
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[A83] Re: rst 20h crap
At 0020h there's a jp to _HLToOP1 (to the real routine, not the equate)
Btw, this routine copies 9 bytes, not 8 as you said.
>From: "The one and only SUCKER ..." <sucker_pvn@hotmail.com>
>Reply-To: assembly-83@lists.ticalc.org
>To: assembly-83@lists.ticalc.org
>Subject: [A83] rst 20h crap
>Date: Tue, 21 Aug 2001 20:41:07 +0000
>
>
>I found out something weird. rst 20h (TI-83-) is the
>same as op1=(hl). So far so good. And rst 20h is the
>same as call 20h. The next rst is rst 28h, so there
>are eight bytes with possible code which is executed
>with rst 20h. At 20h there is: EDB0C90000... , which
>is ldir/ret. If you follow so far, rst 20h should then
>be the same as ldir and the same as op1=(hl).
>But this is not!
>
>for ldir, bc is how many bytes, hl is from where to
>copy to the addres in bc, so bc would have to be eight
>(like eight bytes with possible code in rst 20h) and
>de would point to op1 so that whenever you execute
>ldir, everything would be set to that to copy the
>following bytes at (hl) to op1.
>
>But no!!
>
>What the hell this is about????
>If I think this way everything should match (like replacing stuff)
>But have I made an error??
>
>Here a prmg that uses rst 20h:
>
> ld hl,name
> rst 20h
> call _chkfindsym
> ret nc
> jp _getkey
>;when the prgm AWELCOME exists, and is not protected
>;Done is displayed, otherwise it waits for a key input.
>
>name: .db 5,"AWELCOME",0
>
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