[Coco] [Color Computer] WordPak RS/CO80

[jdaggett at gate.net]

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.