68764C

[Peter Shoebridge]

My EMP20 programmer claims to support this device. If you need to read one,
you could send me the chip and I'd be happy to oblige. Send me private email
(peters at synergration.com) if interested.

Peter

-----Original Message-----
From: Ludis Langens <ludis at netcom.com>
To: diy_efi at coulomb.eng.ohio-state.edu <diy_efi at coulomb.eng.ohio-state.edu>
Date: Sunday, December 14, 1997 2:51 PM
Subject: Re: 68764C


>I found a reference that gives the pin out of the Motorola 68764 8K*8
EPROM.
>Here it is, along with several other EPROMs of a similar size:
>
>2764  TMS2564       68764          TMS2532  TMS2564  2732     2764
>
> VPP      VPP      .......                  VCC               VCC
> A12     ~CS1      :     :                  ~CS2              ~PGM
>                A7 +--_--+ VCC     VCC      VCC      VCC      NC
>                A6 |     | A8
>                A5 |     | A9
>                A4 |  6  | A12     VPP      A12      A11      A11
>                A3 |  8  | ~E/VPP  ~E/~PGM  ~E/~PGM  ~OE/VPP  ~OE
>                A2 |  7  | A10
>                A1 |  6  | A11     A11      A11      ~CS      ~CS
>                A0 |  4  | D7
>                D0 |     | D6
>                D1 |     | D5
>                D2 |     | D4
>               GND +-----+ D3
>
>It looks like you can read a 68764 as if it is a TI TMS2564.  Programming
it
>will be a problem.  None of the standard EPROMs have a (25 volt)
programming
>voltage (VPP) that gets pulsed for each byte.  You could try building an
>adapter socket/circuit that allows it to be programmed as a 2764 or
TMS2564.
>You'll need a transistor that gates the seperate VPP voltage onto pin 20.
>
>Before you build an adapter to the TMS2564 pinout, make sure your
programmer
>can handle it.  My programmer doesn't handle any of the TMS25xx series!  I
>had to build a 2732 to 2532 adapter just to read some 2532s.
>
>                   unsigned long BinToBCD(unsigned long i) {unsigned long
t;
>Ludis Langens         return i ? (t = BinToBCD(i >> 1), (t << 1) + (i & 1)
+
>ludis at netcom.com                 (t + 858993459 >> 2 & 572662306) * 3) :
0;}