Questions tagged [6845]

Questions about the Motorola MC6845 CRT Controller chip, or clones of it (e.g. MOS 6545).

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How does the Motorola MC6845 in the Amstrad CPC 464 behave on start-up?

I'm trying to emulate an Amstrad CPC 464. I'm having trouble to understand how its Motorola MC6845 CRTC chip behaves on start-up. The boot ROM sets up the CRTC registers pretty early on, but if I ...
11
votes
2answers
232 views

Which addresses does the Motorola 6845 CRTC output during retrace?

I'm trying to understand how the video hardware (CRTC and Gate Array) in Amstrad CPCs works. Specifically, I have a question about the behavior of the refresh memory addresses and row adresses output ...
12
votes
1answer
846 views

How did the Commodore PET 80 column display work?

Some variants of the Commodore PET (e.g. the 8000 and 9000 series, as well as some other versions with an aftermarket add-on) produce an 80x25 character display. Their character set is fixed in ROM ...