Re: A83: Fading routine

To: assembly-83@lists.ticalc.org
Subject: Re: A83: Fading routine
From: Stefan Lennartsson <stefan@infinity.hemmet.s-hem.chalmers.se>
Date: Wed, 27 Jan 1999 19:08:22 +0100 (CET)
Delivered-To: assembly-83-outgoing@towerguard.unix.edu.sollentuna.se
Delivered-To: assembly-83@lists.ticalc.org
In-Reply-To: <9499b427.36ae5034@aol.com>
Reply-To: assembly-83@lists.ticalc.org

This routine included loads a picture to the graph buffer and
then fade it from black to normal, it could easily be changed to fade
some other way.

/Stefan

On Tue, 26 Jan 1999 BJTkid@aol.com wrote:

> 
> hello, I am making my first assembly game and I was wondering if it was
> possible to change the contrast on the screen smoothly down and up, so I could
> have smooth transitions in between screens, I have tried several things and I
> was wondering if anyone could tell me how...
> 
> 			-Learning Beginner
> 
>

;undocumented ram adress stores current contrast
;value needs to be modified like this
;	add	a,18h
;	or	C0h
curcont	EQU 8008h

;documented ports
lcdinstport EQU 10h

;documented romcalls
_lcd_busy EQU 4066h
_GRBUFCPY_V EQU 5164h


	ld	a,FFh		;a value that'll make the display dark
	call	_lcd_busy
	out	(lcdinstport),a

        ld      hl,pic
        ld      de,PLOTSSCREEN
        ld      bc,YOUR PICTURE
        ldir
        call    _GRBUFCPY_V

	ld	a,(curcont)
	add	a,18h
	or	0C0h
	ld	b,a
	ld	a,FFh

fadeloop:
	cp	b
	jr	z,CONTINUE
	dec	a
	call	_lcd_busy
	out	(lcdinstport),a
	push	af
	push	bc
        call    _GRBUFCPY_V
	call	_GRBUFCPY_V
	call	_GRBUFCPY_V	;Only delays, on needed
        call    _GRBUFCPY_V
	call	_GRBUFCPY_V
	pop	bc
	pop	af
	jr	fadeloop

References:

A83: Fading routine

From: BJTkid@aol.com