SV: [sdiy] Understanding upgrading SRAM in the 606?

[Andreas H]

When increasing the memory capacity of the 303 for example
with 32 banks all you do is put 32 times bigger chips in
there. It works just like having 32 * 3 original chips which
you in Robins mod switches between using the 5 toggle switches
directly connected to the top 5 adresslines.
when doing a simple memory mod like this dont think in any
hard ways just think of it as adding more chips and selecting
between them using a switch. If anyone ever "cracks" the memory
mapping in the 303 could you share then?
I am writing a sysex dumping pic for my 303 but i have graduation
and millitary service coming up so time will be an issue.
By the way when thinking of the small amount of memory in the 303
I find it hard to belieev that there would be place for any
temporary variables. I find it more possible that ever note
and controll have its own specific adress in the memory step
for step. For example you have 64 patterns each 16 steps
that would make 1024 steps total and thats exactly what the 303
has. then thinking about the fact that you have note on/off
accent on/off slide on/off and a total of 37 half notes which would
take 6 binary bits of memory makes it a total of 9 bits for one
pattern step.
my guess would be that the memory is mapped so that step 1 in pattern 1
in bank 1 has the adress 0 in the memory. step 2 has the adress 1 and so
on. my guess would also be that 2.25 chips are used for patterns while
the last 0.75 chip is track data. but its just a guess until someone proves
me wrong.

/ Andreas H

> -----Ursprungligt meddelande-----
> Från: owner-synth-diy at node12b53.a2000.nl
> [mailto:owner-synth-diy at node12b53.a2000.nl]För Trevor Page
> Skickat: den 2 maj 2001 10:26
> Till: Rob B.; Plutonique9; synth-diy at node12b53.a2000.nl
> Ämne: Re: [sdiy] Understanding upgrading SRAM in the 606?
>
>
> Hi,
>
> To double the amount of memory in your 606, you could indeed
> install another two SRAMs, connect them to the same address and
> data lines. Your toggle switch would select which pair of SRAMs
> the chip select lines are routed to. Or (as I think Robin's mod
> does) replace the existing SRAMs with a larger capacity memory
> device, and use your new bank select switches to toggle the most
> significant address lines.
>
> I assume it's ok to flip between banks while the machine is
> running? I wonder if the CPU uses a small part of the memory for
> temporary variables etc. which it would 'lose' if you flipped to
> another bank, causing things to screw up? Best thing would be to try it.
>
> I've repaired memory -related faults in several TB303's and
> 606's. I'm not too sure about the TR606 here, but I often
> wondered if one of the three SRAMs inside the 303 is also used by
> the CPU for saving temporary variables, etc. associated with the
> currently edited pattern. If I recall correctly, the machine
> wouldn't save/recall any pattern at all if one particular SRAM
> was removed or non-functioning. But remove eiher of the other two
> devices, and certain pattern banks would still work. (I could be wrong).
>
> I've meant to learn exactly how these machines do save data to
> memory, if only I actually had some room to put the logic
> analyzer somewhere... (still stashed away at my parents')
>
> Uh better go do some work now.
>
> Trev
>
> ----- Original Message -----
> From: "Rob B." <cyborgzero at home.com>
> To: "Plutonique9" <Plutonique9 at symbiocom.com>,
> <synth-diy at node12b53.a2000.nl>
> Sent: Wed, 2 May 2001 00:48:52 +0100 (GMT+01:00)
> Subject: Re: [sdiy] Understanding upgrading SRAM in the 606?
>
> > The piggybacking idea works, you just have to reroute the Chip
> > select/read/write lines using a switch. I have thought about
> it, but haven't
> > done it yet for my 606.
> >
> > I assume the 303 is roughly the same.
> >
> > Rob
> > ----- Original Message -----
> > From: "Plutonique9" <Plutonique9 at symbiocom.com>
> > To: <synth-diy at node12b53.a2000.nl>
> > Sent: Wednesday, May 02, 2001 3:32 AM
> > Subject: [sdiy] Understanding upgrading SRAM in the 606?
> >
> >
> > > Hey there,
> > > I wrote about this a little while back, and someone sent me a link to
> > > a schematic detailing an idea for a 32 bank 303 memory mod, not Robin
> > > Whittle's though.
> > >
> > > I'm eager to learn on how the memory in these X0X's work, as both the
> > > 606 and 808 desperately need more pattern data storage.
> > > I don't want to go the big 32 bank mod yet, I'd even be happy with
> > > just doubling the amount of space. I've tried reading up on SRAM, but
> > > I can't find any information that is relevant to understanding how to
> > > increase the banks in these X0X's, or really any instrument for that
> > > manner.
> > >
> > > Is it possible to "piggy back" SRAM on top of the existing memory and
> > > have some sought of toggle switch which chooses between which SRAM is
> > > being used? When you push the bank number "I/II" on the 606, is this
> > > just switching between the 2 sram chips onboard, or are they both
> > > used in both mode "I" and "II".
> > >
> > > I'm sure it is not as hard as maybe I think, but if someone could
> > > point me in the right direction in reading up on this subject, or if
> > > the could clear up some of the "logic" behind how the memory works in
> > > these machines, meaning what the how the Pins are used to select
> > > different banks, etc. I'd be dig it extremely. It is a very confusing
> > > topic to the new comer, much different from straight forward sound
> > > modifications, but I feel this is only because of a lack of resources
> > > on information on the subject.
> > >
> > > Anyways thank you, and could whoever sent me that 303 memory upgrade
> > > schematic link, could you please forward it to me again.....:)
> > >
> > > Seeya
> > >
> > >
> > > -- Plutonique9, Plutonique9 at symbiocom.com
> > >
> > > http://www.mp3.com/Plutonique9
> > >
> > >
> >
>
>
>
>
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