[A83] Re: lcd mem as ram

To: assembly-83@lists.ticalc.org
Subject: [A83] Re: lcd mem as ram
From: Peter-Martijn Kuipers <hyper@@hysoft-automation.com>
Date: Fri, 4 Jan 2002 17:34:31 +0100 (CET)
In-Reply-To: <5.1.0.14.0.20020104123659.0360fc50@pop.home.se> from "Olle Hedman" at Jan 04, 2002 12:49:55 PM
Reply-To: assembly-83@lists.ticalc.org


Then what is x-incrementing and y-incrementing?

> >Could this extra memory be used as an offscreen gfx-buffer for fast 
> >(hardware)
> >scrolling?? (a bit like Mode-X on PC's)
> >
> >just wonderin'...
> 
> nope. the lcd driver only supports vertical hardware scroll. It does this 
> by having a register that says what line in the memory (on the lcd driver) 
> that is the first line.
> it starts reading from this line, and reads on until the end of the ram, 
> then it wraps over and reads the top, until it has read 64 lines.
> Because of this, if you change the offset, your screen image will "wrap 
> around" and come back at top (or bottom, depending on what way you scroll)
> the register is called "z-address", and you change it by writing a value 
> between $40 and $7F to the lcd control port.
> unfortunatly, there is no register for changing the x-offset, so horizontal 
> hardware scroll is not possible.
> which is a bit of a shame, since horizontal scroll in software is the slow 
> one of the two.
> 
> ///Olle
> 
> 
>

Follow-Ups:

[A83] Re: lcd mem as ram

From: Olle Hedman <alh@home.se>

References:

[A83] Re: lcd mem as ram

From: Olle Hedman <alh@home.se>