I have a bunch of small boards that use this baby, but the fact that its
relatively slow and relies on relatively conservative timing makes it easy to
design an application badly and not at all easy to design one well with it.
It saves you having to provide two LS257's and an LS590. I dont' find that
much of a saving. Those are all three 16-pin parts and cost well less than
the 3242 did, regardless of whether you used Intel's or Motorola's. Sadly,
the thing didn't provide much to help you with the timing itself, but that was
pretty easy. There was a companion part, the MC3480, which was helpful with
timing, though, as I said, it helped you do it badly and just got in the way
of doing it well.
I've got the data somewhere, but in a databook and not in a loose sheet.
Dick
----- Original Message -----
From: "Tony Duell" <ard_at_p850ug1.demon.co.uk>
To: <cctalk_at_classiccmp.org>
Sent: Sunday, June 09, 2002 12:58 PM
Subject: Re: Anyone have a data sheet on the MC3242?
> >
> >
> > I'm stripping interesting parts off of these stat mux boards
> > that I recently got around the corner - lots of socketed 6502s
> > and 65c02s, 2532s and the like. Many of the boards have a 24-pin
> > DIP MC3242 which I can find little about - Google only gives me
>
> Intel also made it (or at least they made something called a 3242 with
> the same functions from what I can see).
>
> It's basically the address path logic for 16K DRAMs (7 address lines to
> the RAM). It's a 7-wide 3-input multiplexer and 7 bit counter (for the
> refresh address). The 3 inputs to the mux are the high 7 address inputs,
> the low 7 address inputs, and the output of the counter.
>
> While it didn't make DRAM control easy, it reduced the number of packages
> you needed.
>
> The pinout is :
>
> 1: COunt/ (clock input to refresh counter)
> 2: Refresh Enable (High = address out from refresh counter, low = from
> row/col mux)
> 3: Row Enable (High = row/column mux passes low 7 address lines, low = high
> 7 address lines)
> 4: N/C
> 5: A1 input
> 6: A8
> 7: A2
> 8: A9
> 9: A0
> 10: A7
> 11: O0/ (Address 0 Output, inverted)
> 12: O2/
> 13: O1/
> 14: Gnd
> 15: Zero Detect/ (low if (refresh counter == 0))
> 16: O5/
> 17: O4/
> 18: O3/
> 19: O6/
> 20: A10
> 21: A3
> 22: A11
> 23: A4
> 24: A12
> 25: A5
> 26: A13
> 27: A6
> 28: Vcc (+5V)
>
> > So... anyone have any information on the MC3242 and why I might want
> > to save a couple dozen of them?
>
> Well, I wouldn't design using one now, but it was commonly used on old
> DRAM boards (Acorn used it, I think, in the 'System' machines, I've seen
> it on S100 boards, etc), and thus it might be worth saving a few.
>
> -tony
>
Received on Sun Jun 09 2002 - 16:38:23 BST