[Diy_efi] Continuing the chip switcher "problem"

Tue Feb 15 07:28:46 GMT 2005

More info -  The Not OE line of the eeprom is connected to the not psen
line at pin 23 of the MCU.  Now further looking at this line, there is a
10kohm resistor attached between this line and pin 63 of the mcu which is
the Vref line.  Pulling it to Vref.

Not(Psen) - Program Strobe Enable : The strobe pulse to fetch to external
program memory.

I'm guessing this is the reason the signal looks so strange.  I'm going to
take a look at the signal tomorrow when I can plug it back in the car. 
I'll take some readings right at the MCU.

Marcello

> Ok everybody,
>      I've been doing more homework.  The processor that is driving this
> whole thing is a OKI M66207.  I found datasheets on it.  Would the
> signal I'm trying to find that connects to the not OE line of my
> eeprom be a direct output of the MCU?  I'm trying to trace where this
> line goes so I can confirm whether there is a problem with the signal
> or not.  Perhaps a bad solder or something.
>
> Marcello
>
>
>> Marcello,
>>
>> This chip the 74HC373 is a 'transparent latch'. The Q ouputs follow the
>> D
>> inputs.
>> This is used for demultiplexing the bus Address's from the data.
>> Mostlikely
>> its a 8 bitter in the ECU.
>>
>> It typically does not drive the chip selects.
>> Although it may be used as  a buffer in transparent mode.
>>
>> If you do latch the upper 2 bits use a true latch.
>>
>> Cheers
>>
>> ----- Original Message -----
>> From: <mbelloli at speedymotorsports.com>
>> To: "A list for Do-It-Yourself EFI" <diy_efi at diy-efi.org>
>> Sent: Monday, February 14, 2005 5:15 PM
>> Subject: RE: [Diy_efi] Continuing the chip switcher "problem"
>>
>>
>>> Everyone,
>>>      I got a chance to play a bit this afternoon.  Maybe this piece of
>>> information will help.  When an eprom is installed in the ecu, you
>>> have to install a 74hc373 along with it.  These were both already in
>>> the ecu I am working with so didn't think that much about it.  Here
>>> is a link to a datasheet on that 3-state latch.
>>>
>>> http://www.jameco.com/wcsstore/Jameco/Products/ProdDS/45831.pdf
>>>
>>> Would this chip be supplying the signal to the not OE line? or the not
>>> CE
>>> line?  I'm going to take the ecu home tonight and do some probing.  I'm
>>> just thinking maybe this is the latch I need, and won't need anything
>>> else.
>>>
>>> Thanks,
>>>
>>> Marcello
>>>
>>>
>>>
>>>
>>>
>>> > Have you thought of using several chips the same size as the stock
>>> prom
>> in
>>> > parallel, and using flip-flops/logic to toggle the OE and CE lines to
>>> > enable
>>> > which chip you want?  That was another way I did it on my Buick GN
>> before
>>> > I
>>> > went to a single larger chip... The problem may lie in the fact that
>>> the
>>> > code is in the chip as well as the tables... GM was only tables...
>> Another
>>> > option is see if you cant build a small circuit to multiples one chip
>> with
>>> > the code and a flash for the tables and only change the tables...
>>> >
>>> >
>>> >> -----Original Message-----
>>> >> From: diy_efi-bounces at diy-efi.org
>>> >> [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of
>>> >> mbelloli at speedymotorsports.com
>>> >> Sent: Monday, February 14, 2005 10:49 AM
>>> >> To: A list for Do-It-Yourself EFI
>>> >> Subject: Re: [Diy_efi] Continuing the chip switcher "problem"
>>> >>
>>> >> Will,
>>> >>      Unforunately the image is everything in one.  Both code
>>> >> and tables.
>>> >> I have put a link to the 29c010 on my webpage as well.
>>> >>        http://home.comcast.net/~hexibot43/ChipEnableLogic.htm
>>> >>
>>> >>      I had gone to the Pic Chip because I had a lot of other
>>> >> ideas I'd like to add as time goes by.  I wanted to be able
>>> >> to change to the code on the fly in one bank while running on
>>> >> another bank.  I could then switch it in after the changes
>>> >> and the checksum were calculated.
>>> >>  And I wanted to have a nice display because none of my
>>> >> friends understands what I am doing, but they understand
>>> >> plain english when it is in front of them.  I thought to
>>> >> maybe use a graphic display later, which would allow me to
>>> >> incorporate displaying the tables for fuel and spark.  I also
>>> >> want to later add datalogging capability.
>>> >>      I am thinking could I use this latch with my pic?  I
>>> >> would supply the new hi order address I would like to it, and
>>> >> when the time is right the latch would do the actual switch
>>> >> for me?  That way take the problem of the switching
>>> >> completely away from my pic.
>>> >>      I have another working computer that I have not modified
>>> >> at the shop.
>>> >>  I am going to go put my DSO on the Not OE line and see what I get.
>>> >>
>>> >> Thanks to everyone,
>>> >>
>>> >> Marcello
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
>>> >> > Marcello,
>>> >> >
>>> >> > A further thought on this - can we assume that what you have in
>>> the
>>> >> > 29C010 is the fuel / ignition map ONLY, i.e. no executable
>>> >> code?  If
>>> >> > it contains both, then more complexity is needed, because you only
>>> >> > want to  assert the altered higher address lines when a fuel /
>>> >> > ignition lookup is being  performed.
>>> >> > But
>>> >> > you could still use the simple approach Bevan & I are
>>> >> advocating if
>>> >> > you have four images of the executable code as well, each
>>> >> with  their
>>> >> > own respective map but otherwise identical.
>>> >> >
>>> >> > Regards
>>> >> >
>>> >> > Will Cowell
>>> >> > _______________________________________________
>>> >> > diy_efi mailing list
>>> >> > diy_efi at diy-efi.org
>>> >> > http://lists.diy-efi.org/mailman/listinfo/diy_efi
>>> >> >
>>> >>
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