[Diy_efi] Continuing the chip switcher "problem"

[mbelloli at speedymotorsports.com]

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
>> > _______________________________________________
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>> > diy_efi at diy-efi.org
>> > http://lists.diy-efi.org/mailman/listinfo/diy_efi
>> >
>>
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