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Re: Z80 MC6845 video board examples [message #9861 is a reply to message #9860]

Tue, 12 April 2022 10:29

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi Roger
Yes, that sounds like a prudent idea. Probably could evaluate the schematic to some extent but even that would be easier in KiCAD since the only ones I've seen are hand drawn.

I think a physical prototype would make evaluation most effective since you could take actual measurements to compare for race conditions, etc.

Many of these video board designs have a high-speed portion associated with the dot-clock. The Z180GDC V1 has it too and it can be tricky to pick the right parts to operate at the limits of regular 74LSxx TTL. Sometimes 74F or 74S parts are needed which the Z180GDC has a few of also.

The design for ZRT-80 seems fairly complete with character ROM and monitor ROM images. I am thinking I could probably reduce the part count somewhat using slightly different design and denser components. 6116s and 2114s are pretty tiny SRAMs and takes a bunch to make any amount of RAM memory.

I think I have a ZRT-80 in the basement somewhere. I need to check on that before I launch on this project

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[Message index]

		Z80 MC6845 video board examples By: lynchaj on Wed, 31 March 2021 04:36
		Re: Z80 MC6845 video board examples By: b1ackmai1er on Wed, 31 March 2021 23:25
		Re: Z80 MC6845 video board examples By: nealcrook on Fri, 02 April 2021 12:57
		Re: Z80 MC6845 video board examples By: lynchaj on Sun, 04 April 2021 06:53
		Re: Z80 MC6845 video board examples By: little_john on Sun, 04 April 2021 12:31
		Re: Z80 MC6845 video board examples By: lynchaj on Tue, 12 April 2022 07:30
		Re: Z80 MC6845 video board examples By: norwestrzh on Tue, 12 April 2022 09:50
		Re: Z80 MC6845 video board examples By: lynchaj on Tue, 12 April 2022 10:29
		Re: Z80 MC6845 video board examples By: lynchaj on Tue, 12 April 2022 10:54
		Re: Z80 MC6845 video board examples By: norwestrzh on Tue, 12 April 2022 14:44
		Re: Z80 MC6845 video board examples By: lynchaj on Tue, 12 April 2022 14:55
		Re: Z80 MC6845 video board examples By: plasmo on Tue, 12 April 2022 19:16
		Re: Z80 MC6845 video board examples By: norwestrzh on Wed, 13 April 2022 09:30
		Re: Z80 MC6845 video board examples By: plasmo on Thu, 14 April 2022 07:22
		Re: Z80 MC6845 video board examples By: gkaufman on Thu, 28 April 2022 07:51
		Re: Z80 MC6845 video board examples By: lynchaj on Sat, 30 April 2022 05:20
		Re: Z80 MC6845 video board examples By: etchedpixels on Tue, 17 May 2022 06:09

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