[Gmecm] Converting eprom to eeprom problem

[bcroe at juno.com]

I am wondering how you get a high and a low with dip 
switches, which are single pole single throw (and not 
always reliable).  The usual way is use about a 4.7K 
resistor between the input and VCC for a high.  Then 
short the input to gnd with a switch for a low.
Bruce Roe

4 Oct 2005  Rick McLeod <dunvegan at sbcglobal.net> writes:
> 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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> > > 
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