Newbie Question about working with DRAM

Archiver

Hello,

I'm farely new to all of this. I've gone through some basic circuits
manuals and am becoming more familiar with the BSX2.

I've recently stumbled across some old printer (256K) DRAM chips
GM71C4256A-80, and for nothing more than curiosity I was wanting to
try to write something to them and read from them.

I can't seem to find any documentation on the chip.

Is there some sort of standard for pin settings on chips like these,
or does anyone know where I might be able to find more information on
the chip?

And I guess, most importantly, is this way to hard to do just for fun?

Thanks,
James

Archiver

Ha. If it's what I think it is, yes. DRAM need to be refreshed or they
loose data. Most likely each chip is only one BIT and 8 would be needed for
8 BITs of data. I have some original INTEL Bubble Memory prototyping kits
that would probably be easier to interface. Complete with Bubble memory CPU
and all interface chips. Yours for only $500, I take PayPal.

---

Original Message

---

From: James Climer [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=jhn1Js60S8rSgjNl2uIlW9RzE74DInN5wLwftekwA2DsdLjmECabwa652_kA6KaGYDc8zCGQAH2q]sbumz@y...[/url
Sent: Sunday, October 05, 2003 3:41 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Newbie Question about working with DRAM


Hello,

I'm farely new to all of this. I've gone through some basic circuits
manuals and am becoming more familiar with the BSX2.

I've recently stumbled across some old printer (256K) DRAM chips
GM71C4256A-80, and for nothing more than curiosity I was wanting to
try to write something to them and read from them.

I can't seem to find any documentation on the chip.

Is there some sort of standard for pin settings on chips like these,
or does anyone know where I might be able to find more information on
the chip?

And I guess, most importantly, is this way to hard to do just for fun?

Thanks,
James


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Archiver

DRAM chips typically need a DRAM controller
to 'refresh' the chips every few milliseconds
or so.

Typically they are 1 bit wide -- so you need 8
of them (or nine if using the PC's parity error
detection).

Basically, for the BS2 they are WAY more trouble
than they are worth. If you really must use a
DIP based RAM chip, then SRAM is a much better
way to go. The 2114 chip is still available,
and is 1K x 4 bits (use two for 8-bits) in an 18
pin DIP. They don't need refresh, which is the
big difference between DRAM (needs refresh) and
SRAM.

And, more modern 6264 (8K x 8 bit, 28 pin wide DIP)
and 62256 (32K x 8 bit, 28 pin wide DIP) are
so much easier to interface.
Go to www.digikey.com , and look for 'RAM'.
Then select 8K x 8, and 32K x 8.

--- In basicstamps@yahoogroups.com, "James Climer" <sbumz@y...> wrote:
> Hello,
>
> I'm farely new to all of this. I've gone through some basic
circuits
> manuals and am becoming more familiar with the BSX2.
>
> I've recently stumbled across some old printer (256K) DRAM chips
> GM71C4256A-80, and for nothing more than curiosity I was wanting to
> try to write something to them and read from them.
>
> I can't seem to find any documentation on the chip.
>
> Is there some sort of standard for pin settings on chips like
these,
> or does anyone know where I might be able to find more information
on
> the chip?
>
> And I guess, most importantly, is this way to hard to do just for
fun?
>
> Thanks,
> James

Archiver

Thanks Allan...

-James

--- In basicstamps@yahoogroups.com, "Allan Lane" <allan.lane@h...>
wrote:
> DRAM chips typically need a DRAM controller
> to 'refresh' the chips every few milliseconds
> or so.
>
> Typically they are 1 bit wide -- so you need 8
> of them (or nine if using the PC's parity error
> detection).
>
> Basically, for the BS2 they are WAY more trouble
> than they are worth. If you really must use a
> DIP based RAM chip, then SRAM is a much better
> way to go. The 2114 chip is still available,
> and is 1K x 4 bits (use two for 8-bits) in an 18
> pin DIP. They don't need refresh, which is the
> big difference between DRAM (needs refresh) and
> SRAM.
>
> And, more modern 6264 (8K x 8 bit, 28 pin wide DIP)
> and 62256 (32K x 8 bit, 28 pin wide DIP) are
> so much easier to interface.
> Go to www.digikey.com , and look for 'RAM'.
> Then select 8K x 8, and 32K x 8.
>
> --- In basicstamps@yahoogroups.com, "James Climer" <sbumz@y...>
wrote:
> > Hello,
> >
> > I'm farely new to all of this. I've gone through some basic
> circuits
> > manuals and am becoming more familiar with the BSX2.
> >
> > I've recently stumbled across some old printer (256K) DRAM chips
> > GM71C4256A-80, and for nothing more than curiosity I was wanting
to
> > try to write something to them and read from them.
> >
> > I can't seem to find any documentation on the chip.
> >
> > Is there some sort of standard for pin settings on chips like
> these,
> > or does anyone know where I might be able to find more
information
> on
> > the chip?
> >
> > And I guess, most importantly, is this way to hard to do just for
> fun?
> >
> > Thanks,
> > James