[Coco] [Color Computer] WordPak RS/CO80

[Boisy G. Pitre]

James,

Thanks for the information.  It sheds some light, but I am still 
uncertain where I write the actual character.  R18 and R19 tell the 
6545 which way to set the address lines to the RAM, but now I need to 
know how to get the character into the RAM chip itself.

Boisy

On Jan 5, 2005, at 9:46 PM, jdaggett at gate.net wrote:

> Boisy
>
> try this webpage
>
> http://www.6502.org/users/andre/petindex/crtctest/internals/diffs.html
>
> There is some minor differences between the MC6845, MC6845-1 and the 
> Rockwell
> 6545 and 6545-1 parts. One major difference between the MC6845 and the
> Rockwell 6545 is bit #3 of R8. Setting this bit to "1" will allow the 
> CPU to access the
> video ram by writing to the write only registers R18 and R19. When the 
> E clock is
> low the MA0 to MA13 address lines will be mapped to the video address 
> address.
> When the E clock is high the MA0 to MA 13 address lines will have the 
> address in
> R18 and R19. This  only works on the Rockwell parts and not the 
> Motorola parts.
>
> james
>
>
>
> On 3 Jan 2005 at 19:12, Boisy Pitre wrote:
>
> From:           	Boisy Pitre <boisy at boisypitre.com>
> Subject:        	Re: [Coco] [Color Computer] WordPak RS/CO80
> Date sent:      	Mon, 3 Jan 2005 19:12:04 -0600
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>>
>> There is a 6116 (2Kx8) RAM chip onboard which connects to the 6545, as
>> well as a 2K Character ROM.
>>
>> It appears that $FF78 and $FF79 are mirrored at $FF76 and $FF77.  So
>> now all that needs to be done is to solve the mystery of how to write
>> characters to the internal RAM so that they are displayed on the
>> screen.
>
>
>
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--
Boisy G. Pitre
E-Mail: boisy at boisypitre.com
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