4 Dec
2024
4 Dec
'24
10:13 a.m.
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