[Diy_efi] Another Eprom Question

Wed Jan 26 04:20:56 GMT 2005

Hi guys

this topic came up many years ago on this list .....im not sure how far back the
archives go but i did explain in depth back then.  Its been a while since i did
a bank of 4 .....done many 2 way but the major problems were:

all 4 eprom images need to be from the same base profile then mods made

debound curcit or judt pull down resistors need to be used to stop the ripple
effect of the switching

make sure you have a good +5 volt into the new chip.  

you should not need to use the CE for switching at all .....all switching should
be done from the top 2 address lines .....dig through the archives ...  I did
post drawings for all to use.  If not i will see if i can dig em up.

Justin

Quoting mbelloli at speedymotorsports.com:

>      Ok, I just checked that the access times.  The stock original chip
> had no better than a 150ns access time.  My 29C010 has a 70ns access
> time.  So I've got that covered.  I'm better than 1/2 the original
> access time.
>  Mab
> > What's the access time on the 29C010?  is it as fast or faster than the
> > original EPROM?  if not that could be the problem.
> >
> >
> > -------Original Message-------
> >
> > From: mbelloli at speedymotorsports.com
> > Date: 01/25/05 20:00:42
> > To: A list for Do-It-Yourself EFI
> > Subject: Re: [Diy_efi] Another Eprom Question
> >
> > I sure hope not!  I'm really trying to get this all set up to do minut
> > changes on the fly.  I need an eeprom to be able to do that.  Soon enough
> > here I'll have it so I just am changing a small part of the whole program
> > instead of the whole thing.  I want to be able to make changes to the
> > fuel
> > table, and spark table while driving.  Not just switch out one chip for
> > another.
> > Thanks,
> > Marcello
> >
> >> wonder if part of the problem isn't the 29C010...  I'd try it with a
> >> 27C010
> >> and see if you have the same problem...
> >>
> >> -------Original Message-------
> >>
> >> From: mbelloli at speedymotorsports.com
> >> Date: 01/25/05 18:17:19
> >> To: A list for Do-It-Yourself EFI
> >> Subject: Re: [Diy_efi] Another Eprom Question
> >>
> >>      That is basically what I have now, but it is setting the check
> >> engine.  And you will have basically a prom error, and the vehicle
> >> running off something other than the chip.  It runs like crap.  This
> >> is in a 1993 Acura Integra with a GSR motor, and a p28 computer.
> >> Stock came with a 27C256.  It already had an eprom in it.  Now it
> >> doesn't do it every time.  I like every third time it will set the
> >> check engine lamp.  you'll have to clear codes, or disconnect the
> >> battery to get it running correctly again.
> >>
> >> Thanks,
> >>
> >> Marcello
> >>
> >>>  Back in 87 I was running a 27C512 with 4 programs on my Buick GN...
> >>> had a small board the chip was on and a shielded ribbon going to the
> >>> ECM.
> >>> would toggle the 2 highest address bytes with a thumbwheel on the dash
> >>> to
> >>> change banks and did it on the fly all the time with no CE light.
> >>>
> >>>
> >>> -------Original Message-------
> >>>
> >>> From: mbelloli at speedymotorsports.com
> >>> Date: 01/25/05 15:13:07
> >>> To: diy_efi at diy-efi.org
> >>> Subject: [Diy_efi] Another Eprom Question
> >>>
> >>> Hello everyone,
> >>> I have been pulling my hair out trying to figure out another one of
> >>> these chipping ideas. I am trying to set up a controller to allow
> >>> the switching of which chip the ecm of a car computer is running on
> >>> the fly while driving. Currently I've got it working very well if
> >>> you switch with the key off, but not while running. The original
> >>> chip was a 27C256, which switched out for an ATMEL AT29C010. I
> >>> really only wanted 4 choices, which this chip more than allows. I am
> >>> trying to set it up so I can have pic processor do the switching for
> >>> me. I cound't put a picture of the waveform that is driving me crazy
> >>> here so I put it on my website at
> >>>
> >>> https://home.comcast.net/~hexibot43/ChipEnableLogic.htm
> >>>
> >>> I just can't understand why it is working right now with the signal I
> >>> have
> >>> on the Output enable pin. From what I understand it shouldn't be
> >>> working,
> >>> but it is working. I thought I was going to simply look at the signal,
> >>> and see drops to ground like I did with the last car computer I looked
> >>> at.
> >>> I figured I could use that as a trigger for an interrupt the would in
> >>> turn wait a set amount of time and then switch banks. This way I could
> >>> do
> >>> the switching when the chip was not be read from, and so the ecm would
> >>> be
> >>> happy and not throw an check engine lamp at me.
> >>> Can anybody sheld some light on this for me? You guys did so well
> >>> helping me last time, I hope you can do it again. And yes, I still
> >>> have a lot more to learn.
> >>>
> >>> Thanks,
> >>>
> >>> Marcello
> >>> _______________________________________________
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