Re: A83: Routine Help, Clearing Section of Graph Buffer... =P

To: assembly-83@lists.ticalc.org
Subject: Re: A83: Routine Help, Clearing Section of Graph Buffer... =P
From: "Evil Sam" <evil_sam@hotmail.com>
Date: Sun, 07 Feb 1999 14:42:49 PST
Delivered-To: assembly-83-outgoing@towerguard.unix.edu.sollentuna.se
Delivered-To: assembly-83@lists.ticalc.org
Reply-To: assembly-83@lists.ticalc.org


>Whats wrong with this short routine...? =P  I want to be able to clear 
the
>first 8 Bytes of Every line of the Graph Buffer, and avoid affecting 
the last
>4 Bytes on every line.  This freezes, but does not crash, my calc for 
some
>reason. I do not see the problem... :\  I would like some assistence 
here
>please, thanks... =P
>
>--Jason K.
>
>Erase_Board:
>	ld hl, PLOTSSCREEN
>	ld de, 5
>	ld bc, 63
>Erase_Loop_1:
>	push bc
>	ld b, 8
>Erase_Loop_2:
>	ld (hl), 0
>	inc hl
>	DJNZ Erase_Loop_2
>	pop bc
>	add hl, de
>	DJNZ Erase_Loop_1
>	ret

  Shouldn't it be "ld de,4". 8+5=13... so your routine is writing to an 
area past PLOTSSCREEN causing a crash.
   Also shouldn't it be "ld b,64" instead of "ld bc,63", I don't know 
maybe 63 is right, but you should use an 8 bit register.


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