Re: A86: Efficiency Problem Part III

To: assembly-86@lists.ticalc.org
Subject: Re: A86: Efficiency Problem Part III
From: ComAsYuAre@aol.com
Date: Tue, 15 Dec 1998 14:46:48 EST
Delivered-To: assembly-86-outgoing@towerguard.unix.edu.sollentuna.se
Reply-To: assembly-86@lists.ticalc.org


In a message dated 12/15/98 12:01:51 AM Eastern Standard Time,
ZeromusMog@aol.com writes:

> There must be an easier way... is there a way to inverse a portion of the
>  screen?


sure.  screen memory starts at $fc00 and goes until $ffff.  just do this to
invert the byte at hl:
	ld a,(hl)
	cpl			;one's complement
	ld (hl),a

you can do this in a loop for inverting a bunch of lines:
	ld hl,$fc00
	ld b,16*7		;7 lines, 16 bytes each
invert_loop:
	ld a,(hl)
	cpl
	ld (hl),a
	inc hl
	djnz invert_loop
	ret

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