[Coco] Re: Re: [Color Computer] Re: Adapter from Coo3 to SVGA

[jdaggett at gate.net]

Kevin

To use say $FF24 to $FF27, you would have to break the line from 
pin#13 of the 74LS138 to pin#23 which is CS2 and not CS0 as in 
my other post. In that break you would have to put some other logic 
to disable the PIA chip and then add glue logic to decode from 
$FF24 to $FF27.

A typical circuit would be "nand" the select line from the 74LS138 
with the A5, inverted A4, inverted A3, and A2 lines. That would 
require a 5 input nand gate with two inputs inverted. This would go 
to a chip enable or select line. Then the A0 and A1 lines can select 
the four individual addresses. 

james


On 6 Apr 2005 at 10:57, Kevin Diggs wrote:

Date sent:      	Wed, 06 Apr 2005 10:57:45 -0700
From:           	Kevin Diggs <kevdig at hypersurf.com>
To:             	CoCoList for Color Computer Enthusiasts 
<coco at maltedmedia.com>
Subject:        	Re: [Coco] Re: Re: [Color Computer] Re: 
Adapter from Coo3 to SVGA
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>

>  If 
> not could we just use $ff24-$ff27 for output?