[Coco] GIME Scrolling Questions

[jdaggett at gate.net]

Chris

The registers $FF9D and $FF9E are the upper 16 address bits of 
the 19 bit memeory address (A18 downto A3). Register $FF9C 
lower nibble is the four bits for Vertical scroll.

james


On 27 Jan 2004 at 2:36, Chris Spry wrote:

From:           	"Chris Spry" <bugster at cedarcomm.com>
To:             	"CoCoList for Color Computer Enthusiasts" 
<coco at maltedmedia.com>
Subject:        	Re: [Coco] GIME Scrolling Questions
Date sent:      	Tue, 27 Jan 2004 02:36:18 -0800
Send reply to:  	CoCoList for Color Computer Enthusiasts 
<coco at maltedmedia.com>
	<mailto:coco-
request at maltedmedia.com?subject=unsubscribe>
	<mailto:coco-
request at maltedmedia.com?subject=subscribe>

> Nevermind I think. Something hit me in the afternoon to give a try
> with the two GIME registers, so I reprogrammed my test program and low
> and behold the idea worked.  Now I got scrolling.  Now I just need to
> figure out a way to program it from shifting up a line with the scroll
> (the 2 registers do reset after a full screen has scrolled by, but at
> the reset the screen goes back to the normal area and then jumps up a
> line again....maybe if I start the FF9D really high and lower it along
> with FF9E bit by bit when needed it'll adjust and won't
> happen.....something to try).  I would love to get less than 4 pixels
> per scroll movement if possible, but this does work for now and if I
> can't it won't kill me. :)
> 
> -Chris
> 
> ----- Original Message ----- 
> From: "Chris Spry" <bugster at cedarcomm.com>
> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
> Sent: Monday, January 26, 2004 6:14 PM Subject: [Coco] GIME Scrolling
> Questions
> 
> 
> > Hey guys,
> >
> > Well I've decided to go in a bit of a different direction with
> > MiniHog and will have a quick scrolling game but the gameplay is
> > going to be different than originally planned.  I was messing around
> > with the GIME scrolling registers quite a bit on Sunday and could
> > not quite figure them out.  I
> was
> > using a standard 320x192x16 screen (HSCREEN 2). I could get the
> > screen to scroll the contents from left to right by poking FF9E and
> > FF9F rather seperately or together in different steps.  Usually
> > steps of 1.  However when using FF9F (Horizontal Offset Register) it
> > would scroll the screen by four pixels per step (Poking with a value
> > of 0-127 sets the horizontal offset address in a different location
> > at a video location x2 of the value being inputed).  It would work
> > up to a point.  First off I noticed the oncoming screen would be
> > shifted up by one line but would scroll fine
> until
> > the value going into FF9F went past 48.  Once it went past there it
> > would lower the line back down and start showing a different
> > location.  I found that out by actually drawing a slope across the
> > screen and then add to
> this
> > slope by 4 horizontal boxes all the way to the left, adding to it to
> > the right after the scroll looking like it's ascending (since the
> > screen
> shifts
> > over by 4 per step).  Then after the 48 value it was as if it wasn't
> taking
> > my boxes anymore and just showing some of the original stuff from
> > before.
> I
> > tried FF9E and it seems to work alright, except that it scrolls too
> > much
> too
> > fast for what I need.  I tried combining the two poking different
> > values
> and
> > getting odd results depending on what I did.  I tried to find the
> > formula
> to
> > make a smooth side scrolling effect adding oncoming new screen data,
> > but can't figure out what this might be if there is one.  I image
> > that there
> is
> > one, especially after seeing Sock Master's scrolling/game demo.  Can
> anybody
> > possible help me out with this, I'd really like to get this game
> > going in production again.
> >
> > -Chris
> >
> >
> > -- 
> > Coco mailing list
> > Coco at maltedmedia.com
> > http://five.pairlist.net/mailman/listinfo/coco
> 
> 
> -- 
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco