[Gmecm] Converting eprom to eeprom problem

[Rick McLeod]

Why would you not just use signal ground as the logic
level low, I've done that for years when I had a
bigger address buss than I needed/could address, which
is your scenario. VCC and SigGND switched w/ dip
switch should work just fine. What about the rest of
the signals for the EEPROM, make sure you have tied
the program/erase lines to the appropriate levels. The
action you are getting makes me think (I'm not sure of
the code in the ECM you have) that it is checksum
error'ng, is the program you are using fouling the
checksum bits, or is this even appropriate for your
ECM, I'm not sure, just an idea.

Your approach is sound, Moates has been doing that w/
other ECM/PROMs as I recall, might check his site for
some insight.

Good luck!


--- Darryl M Gilbert <dgilbert78 at juno.com> wrote:

> Hmmmmm, should work. Do you have a bypass cap
> between Vcc and gnd right
> at the chip?? I would have to look at the chip specs
> to see whats up, but
> sounds logical. Make sure when you switch from one
> to the other no pins
> are left floating, you know, not connected to
> anything. All pins should
> be terminated, never floating
> good luck
> darryl..
> On Tue, 04 Oct 2005 20:05:33 -0500 Mike Poore
> <mp at FlowersByValerie.com>
> writes:
> > I have an '870 ecm that has a 2732 eprom. My goal
> was to make a new 
> > board that I would allow me to use a 2864 eeprom.
> I have soldered in 
> > a 
> > new dip socket and remotely located the (e)eprom
> to a new board with 
> > dip 
> > switches to allow for using a 2732 or the 2864.
> The dip switches are 
> > 
> > configured to allow usage of the lower 32k or
> upper 32k of the 2864 
> > 
> > thereby tricking the ecm to think a 2732 is
> installed.
> > 
> > My theory is that if I could provide either a high
> or low signal to 
> > A12 
> > (pin 2 on the 2864), via the dip switches, then
> the ecm would 
> > address 
> > A0-A11 as normal. That would then allow the 2864
> to be split into 
> > banks 
> > of 32k.
> > 
> > I have run tests and the 2732 works fine, so I
> know that there are 
> > no 
> > problems with noise or wiring of the circuit in
> this configuration. 
> > I 
> > copied the same bin to the lower half of the 2864.
> To provide high 
> > and 
> > low signals to A12 of the 2864 to read the 2864, I
> used Vcc (pin 24) 
> > of 
> > the 2732 socket connected to A11 (pin 2) of the
> 2864 to provide a 
> > high 
> > signal and used a low signal from Chip Enable (pin
> 18) of the 2732 
> > socket.
> > 
> > Using the above circuit, the ecm works very
> briefly and then the ses 
> > 
> > light starts blinking very quickly, which seems to
> indicate a memory 
> > 
> > problem. That low signal from the Chip Enable
> circuit seems to be a 
> > problem.
> > 
> > Before going any further, can anyone offer an
> opinion as to wether 
> > the 
> > Chip Enable pin is a reliable low signal source,
> and if not, suggest 
> > a 
> > better way to get a low signal to A12. I have not
> tried using the 
> > upper 
> > 32k yet, so I am also very interested in any
> opinions on using Vcc 
> > as a 
> > high signal for A12.
> > 
> > I am an electronics novice, so if you have a
> solution, please be 
> > detailed. For example, if you told me I need a
> pull-up resistor, I 
> > know 
> > the principle behind it, but could not figure out
> how to include it 
> > in 
> > my circuit. In other words, I know enough to be
> dangerous.
> > 
> > Thanks, Mike
> > _______________________________________________
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> > http://lists.diy-efi.org/mailman/listinfo/gmecm
> > 
> > 
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