Atom MC6847 noisekiller

discussion of games, software, hardware & emulators relating to the Acorn Atom
herklots
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Atom MC6847 noisekiller

Postby herklots » Wed Jan 16, 2013 10:53 pm

Here's the original info on the Alan Knowles's design for the screen noise eliminator for the Atom. I bought one of his boards back in the day...

Also a good quality OCRed scan of the MC6847 data sheet for those who don't have it.

Regards,
Tim Herklots

herklots
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Re: Atom MC6847 noisekiller

Postby herklots » Wed Jan 16, 2013 10:58 pm

Trying to add the files again...

herklots
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Re: Atom MC6847 noisekiller

Postby herklots » Wed Jan 16, 2013 11:19 pm

Ok, so now I realise zip good pdf bad :)
Attachments
MC6847.zip
(1.6 MiB) Downloaded 67 times
A E Knowles Atom Screen Noise Eliminator.zip
(822.85 KiB) Downloaded 98 times

herklots
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Re: Atom MC6847 noisekiller

Postby herklots » Wed Jan 16, 2013 11:30 pm

While I'm at it, here's a pdf of Splitting the Atom which I scanned from my well used copy... part 2
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Splitting the Atom part 2.rar
(4.68 MiB) Downloaded 230 times

herklots
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Re: Atom MC6847 noisekiller

Postby herklots » Wed Jan 16, 2013 11:31 pm

Splitting the Atom part 1
Attachments
Splitting the Atom part 1.rar
(1.92 MiB) Downloaded 281 times

Prime
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Re: Atom MC6847 noisekiller

Postby Prime » Thu Jan 17, 2013 9:44 am

That's basically the noiskiller that is included on the Colour board, the circuit was suggested to me by Kees, who had seen it reprinted in a Dutch Atom newsletter.

I modified the circuit slightly and used an LS573, as it's the same chip as the 373 but has a more convenient pinout (inputs and outputs on opposite sides of the chip). I also replaced the diodes which act as an AND gate with a proper LS 08, which I then had to modify to use LS00 nand gates when it became obvious that I needed to disable this circuit if using the clock doubler (on the RAM-ROM), which is why the patches to the back of the board :)

One final note, is that different manufacturers LS/HC/HCT 123 chips have slightly different time constants, and the R and C values have to be calculated from the datasheet of the chip you are using.

Cheers.

Phill.

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hoglet
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Re: Atom MC6847 noisekiller

Postby hoglet » Thu Jan 17, 2013 10:46 pm

Hi Tim,

I'm not sure if you posted this in response to my question in the Atom Colour Board thread, but thanks - this is exactly what I was looking for.

It's a bit of a weird co-incidence, but I actually knew Alan Knowles back in the '80's. He was a lecturer on Computer Engineering at Manchester University and taught me hardware design. Really nice chap.

Dave

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Other Alan Knowles Atom stuff

Postby herklots » Fri Jan 18, 2013 12:53 am

Alan passed me all his stuff some years ago. Here are his two ROM designs and his ROM pager. Everyone is welcome to make use of them. I probably have the source code printouts too; there's a mess of white/green dot matrix printouts, so getting the correct version won't be easy. I'm sure Alan would be tickled pink that there's interest after all these years...

Tim
Attachments
AEK Monitor ROM 1.0E.zip
(518.38 KiB) Downloaded 54 times
A E Knowles ScreenROM v1.3.zip
(462.57 KiB) Downloaded 54 times
A E Knowles Atom 8 way ROM pager.zip
(64.04 KiB) Downloaded 59 times