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Atom MC6847 noisekiller

Posted: Wed Jan 16, 2013 10:53 pm
by herklots
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

Re: Atom MC6847 noisekiller

Posted: Wed Jan 16, 2013 10:58 pm
by herklots
Trying to add the files again...

Re: Atom MC6847 noisekiller

Posted: Wed Jan 16, 2013 11:19 pm
by herklots
Ok, so now I realise zip good pdf bad :)

Re: Atom MC6847 noisekiller

Posted: Wed Jan 16, 2013 11:30 pm
by herklots
While I'm at it, here's a pdf of Splitting the Atom which I scanned from my well used copy... part 2

Re: Atom MC6847 noisekiller

Posted: Wed Jan 16, 2013 11:31 pm
by herklots
Splitting the Atom part 1

Re: Atom MC6847 noisekiller

Posted: Thu Jan 17, 2013 9:44 am
by Prime
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.

Re: Atom MC6847 noisekiller

Posted: Thu Jan 17, 2013 10:46 pm
by hoglet
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

Other Alan Knowles Atom stuff

Posted: Fri Jan 18, 2013 12:53 am
by herklots
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