[Coco] Re: [Color Computer] CoCo 2 questions.

jdaggett at gate.net jdaggett at gate.net
Thu May 12 17:57:59 EDT 2005


The 783 has an 8 bit refresh counter but only outputs 7 bits. The 
785 must then output the 8 the refresh bit through Z7 to allow 256 
col refresh.  

Also the difference between the 6822 and the 6821 is that the 6822 
has open drain outputs on the ports. These can withstand up to 18 
VDC on them and require pullups when configu red as outputs. 
Otherwise they operate the same and are pin indentical. 


On 12 May 2005 at 17:35, Mike Pepe wrote:

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From:           	Mike Pepe <lamune at doki-doki.net>
Date sent:      	Thu, 12 May 2005 17:35:02 -0400
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CoCo 2 questions.
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> Functionally identical with the major difference being the 785
> supports 256 column refresh RAMs (like 4164) whereas the 783 has a 7
> bit counter and only can refresh 128 column (max) rams.

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