Date   : Mon, 07 Feb 2005 21:03:24 +1300 (NZDT)
From   : Michael Foot <mjfoot@...>
Subject: Re: BBC SWRAM module

Quoting John Kortink <kortink@...>:

> On Sun, 6 Feb 2005 03:12:04 +0000 (GMT), Greg Cook wrote:
> 
> >[...]
> >
> >The yellow wire is sampling /R/W (SRAM mods normally take R//W from a
> >nearer pin) but there are spare gates on the "module" to invert the
> >signal.
> 
> It samples NR/W nand 2MHzE, which makes for a cleaner and
> safer write strobe, because it is then synced to the data
> transfer part of the bus cycle, as it should be (instead
> of relying on accidental 6502 behaviour of defaulting to
> 'read' on R/nW).

Thanks for all the info so far. I've uploaded a much better photo:
http://homepages.paradise.net.nz/mjfoot/SRAM_2.jpg

I agree that it's a homemade job and that whoever did it knew what they were 
doing. I've not seen a schemetic for this type before but it looks overly 
complex to me. The green wire going to S37 is interesting.
Unfortunately because it is an Econet only machine, I've not go around to 
testing it out yet. 

Cheers,

Mike.

--
Michael Foot <mjfoot(at)paradise(dot)net(dot)nz> *
http://homepages.paradise.net.nz/mjfoot/
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