[Diy_efi] Continuing the chip switcher "problem"
Martin E
martine001 at verizon.net
Mon Feb 14 12:07:25 GMT 2005
Marcello,
I see you made a jumper, 6 inches long for the 29F010. You may have a
unconnected pin at the OE of the chip. Or even a bad socket.
Otherwise the other waveforms look good.
I would implement a latching system, this would solve your Check engine
light. Even if there is code mixed in with your fuel map.
Cheers
Martin
----- Original Message -----
From: <mbelloli at speedymotorsports.com>
To: "A list for Do-It-Yourself EFI" <diy_efi at diy-efi.org>
Sent: Sunday, February 13, 2005 11:43 PM
Subject: Re: [Diy_efi] Continuing the chip switcher "problem"
> Ok, I finally got a chance later in the day to take some snapshots of
> the waveforms on some of the lines on my AT29C010. I'm starting to
> wonder about my DSO. It is a 5MegaSample unit, and the smallest time
> setting is 5microsecs. And this is the setting I'm having to take
> most of my readings. I wondering if it is really capable of
> displaying true waveforms at the extreme limit of its setting. I
> just can't figure why all the other pins I'm looking at on the chip
> look reasonable. The only one that is giving me trouble is the one I
> need to figure out.
>
> http://home.comcast.net/~hexibot43/Waveforms.htm
>
> Any ideas? Marcello
>
>
> > It may only care about the difference it has between it's VSS pin and
> > the other pins, but if there is voltage or noise riding on the VSS, then
> > the PCM is going to see that noise Plus the signals coming in and out of
> > the chip superimposed... and that will play havoc with things.
> >
> >
> > On Sat, 2005-02-12 at 19:51 -0500, mbelloli at speedymotorsports.com wrote:
> >> I'll do some checking again tomorrow with the DSO. I'll take some
> >> readings of my chassis ground to Vss. And I'll take a reading from
> >> Vcc to chassis ground, and to Vss. It is baffling me. The last car
> >> I did confused my at first, but with some help I understood it. This
> >> one is not making any sense. I figured the eeprom only knows the
> >> difference between any pin, and its Vss pin. So, if the waveform I
> >> have is representative of that diffenence I would have my answer.
> >> But it looks way wrong. Maybe tomorrow I'll have the answer when I
> >> check it again. Thanks, Marcello
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> > Marcello,
> >> >
> >> > Looks like your Vss isnt exactly gnd, Is the probe gnd lead tied to
> >> the
> >> > chassis or to the Vss pin on the Eprom? What is the DC between the
Vss
> >> pin
> >> > and Chassis? Thats one ugly waveform ;)
> >> >
> >> > There might also be some odd ball ground offset design. particulary
> >> for
> >> > the
> >> > injector drivers so that the Fet gates get a negative voltage to turn
> >> off.
> >> >
> >> > And Yes the OE is where the read strobe would be connected, unless by
> >> > design
> >> > the OE is tied to gnd. This might be done if the Eprom is the only
> >> thing
> >> > in
> >> > the memory map. The read strobe should still be availble on the Uc.
> >> >
> >> > Cheers
> >> > ----- Original Message -----
> >> > From: <mbelloli at speedymotorsports.com>
> >> > To: "A list for Do-It-Yourself EFI" <diy_efi at diy-efi.org>
> >> > Sent: Saturday, February 12, 2005 2:00 AM
> >> > Subject: Re: [Diy_efi] Continuing the chip switcher "problem"
> >> >
> >> >
> >> >> I think I'm following what is being said. Now here is a link
to
> >> my
> >> >> web page with all the info on my chip switcher.
> >> >> http://home.comcast.net/~hexibot43/ChipEnableLogic.htm
> >> >> I was thinking that I should be doing the switching during the
> >> time
> >> >> that no read was occuring. Now we're saying that I should do it
> >> >> immediately after a read occurs. Does that mean when I see the
> >> >> moment of a read I immediately do my switch? Whatever immediatley
> >> >> means. I'm hoping everyone will look at the waveform I'm seeing on
> >> >> my Output Enable pin, and see if they can give me any insite. I'm
> >> >> very confused by it. I swear it never gets near ground. Help me
> >> >> ObiWan your my only hope....Marcello
> >> >>
> >> >>
> >> >>
> >> >>
> >> >>
> >> >> > Martin,
> >> >> >
> >> >> > I absolutely agree. There isn't a problem if normal good practice
> >> is
> >> >> > followed. I used to be a hardware designer and would never think
> >> of
> >> >> > changing
> >> >> > addresses without "locking in" those changes to the read cycle.
> >> The
> >> >> > address upper
> >> >> > bits (used for bank switching) should always be stable during a
> >> read.
> >> > If
> >> >> > they aren't latched, there's likely to be trouble. And since it
> >> is
> >> >> so
> >> >> > simple
> >> >> > to do, any quad latch will do it, there really seems no reason
not
> >> >> to.
> >> >> > The
> >> >> > chip data sheets are available, I have to assume - I'm no longer
> >> > working
> >> >> > as an
> >> >> > engineer.
> >> >> > Good luck and best wishes
> >> >> >
> >> >> > Will Cowell
> >> >> >
> >> >> >>Marcello,
> >> >> >>
> >> >> >>As an electrical engineer, I would say that it would be wise to
> >> >> Latch
> >> >> >> your
> >> >> >>bank switching bits on the rising edge of the read strobe. This
> >> way
> >> >> the
> >> >> >>address will not change during a READ (usually active low). Ugly
> >> >> things
> >> >> >> will
> >> >> >>happen and you may not meet the setup and hold times for the
Flash
> >> >> >> memory.
> >> >> >>Also if the bank switching wires are 'long' you may be coupling
in
> >> > noise
> >> >> >> to
> >> >> >>the ECM, as well as switch bounce noise.
> >> >> >>
> >> >> >>cheers
> >> >> >>Martin
> >> >> >
> >> >> > ----- Original Message -----
> >> >> > From: <mbelloli at speedymotorsports.com>
> >> >> > To: <diy_efi at diy-efi.org>
> >> >> > Sent: Thursday, February 10, 2005 6:46 PM
> >> >> > Subject: [Diy_efi] Continuing the chip switcher problem
> >> >> >
> >> >> >
> >> >> >> Hello Everyone,
> >> >> >> I had asked the question eariler in regards to creating a
> >> > multiple
> >> >> >> bank chip switcher for an ecm. Everyone basically said I should
> >> be
> >> >> >> able to just switch the chip without any regard for whether the
> >> chip
> >> >> >> is being accessed during the switch. I finally got my pic chip
> >> >> >> controller up and running. I'm running at 20mhz, and when I do
a
> >> >> >> switch I'm still getting a check engine light. 2 out of three
> >> >> times.
> >> >> >> Thinking about this, I put the same exact bin in each of the
> >> banks
> >> >> >> of the chip, and still get the same response. Could it not be
> >> that
> >> >> >> I'm switching in the middle of a read, and that is causing this
> >> >> >> problem??? What does everyone think. If I turn the car off,
and
> >> do
> >> >> >> the switch no problem. I'm using this on a 1991 acura
> >> >> integra....had
> >> >> >> a 27c256 as the base chip, and I'm using a 29c010 as the
> >> >> replacement.
> >> >> >> I'm controlling the highest two address lines as bank select
for
> >> a
> >> >> >> total of 4 banks.
> >> >> >> I'll put the info for chip changer on my website, and add a
> >> >> link
> >> >> >> to
> >> >> >> it tonight.
> >> >> >>
> >> >> >> Any ideas???
> >> >> >>
> >> >> >> Thanks,
> >> >> >>
> >> >> >> Marcello
> >> >> >
> >> >> > _______________________________________________
> >> >> > diy_efi mailing list
> >> >> > diy_efi at diy-efi.org
> >> >> > http://lists.diy-efi.org/mailman/listinfo/diy_efi
> >> >> >
> >> >>
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> >> >>
> >> >
> >> >
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> >>
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