Re: LZ: Screen Reversing...

Subject: Re: LZ: Screen Reversing...
From: Ilkka Neuvonen <pdx@kontu.bbs.fi>
Date: Wed, 9 Oct 1996 23:55:48 +0200 (EET)
In-Reply-To: <199610082239.PAA08449@eagle.ns.net>

On Mon, 8 Oct 1996, Ben Shakal wrote:


> > > I want to add screen reversing to my etch a sketch thing... i have the code 
> > > from another program but it is uncommented can someone send me a commented 
> > > version of screen reversing! (pixel on to pixel off and vice versa)
> > 
> > well.. (writing on-line, so prolly not 100% error-free) 
> > 
> > ; ------ clippityclippityclip ------------------
> > 
> >   [a bunch of code]
> > 	neg             ; a=0-a, so all 1->0 and 0->1
> 
> According to my Z80 programming book, this instruction will flip all 
> the bits and then add one:
>         in:  0101 1010
>         out: 1010 0110
> What might work is the cpl instruction.  Hope this helps!


Whoops... Sorry... Maybe I should've thought a bit... When it said 0-a, i 
read $FF-a... my mistake...


   -Pyrone

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