4 Dec
2024
4 Dec
'24
10:24 a.m.
Tony,
Thank you for the education. I did some minimal programming of the 6847
on the CoCo and nothing really on the 6845.
A majority of the 6809 programming that I did was for Gimix, when I
worked there in the early 1980's.
And then on embedded 6809 based system, also in the early 1980's.
Mike
On 12/4/2024 12:13 PM, Tony Duell wrote:
On Wed, Dec 4, 2024 at 5:58 PM Mike Katz
<bitwiz(a)12bitsbest.com> wrote:
You are correct. The 6845 was monochrome and the
6847 was the color chip.
The 6845 was called the 'CRT Controller'. It was
basically a set of
programmable counters that would address the video RAM, generate sync
signals, latch the address if a lightpen detected a 'hit' and so on.
It did not do anything with the data from the video RAM, that was
handled by other circuitry. It could certainly be used in colour
systems, the BBC micro, IBM CGA card and so on.
The 6847 was the the video display generator. It could generate the
video addresses and timing (e.g. the Acorn Atom) but didn't have to.
It did handle the data from the video RAM, it had an internal
upper-case only character generator, block graphics, etc. It did
generate colour video.
-tony