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Author Topic: 29f800bb hardware switch  (Read 6730 times)
papasound
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« on: May 02, 2013, 08:01:24 AM »

Hi
i want to have 2 flash memories on one ecu switchable by hardware switch.
I know it can be done. I can unsolder the chip, solder in that place a socket,
then solder together two chips except some pins that would be switchable.
The question is which pins is switchable for 29F800BB.

The chip i can buy in my local store is AM29F800BB-55EF SO,
that should be fine. datasheet attached.
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ddillenger
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« Reply #1 on: May 02, 2013, 08:41:07 AM »

There's more than enough room on the chip to do sowftware switcing, and several routines posted here that do just that. If hardware switching is what you're after, that too is discussed. As long as the chip is the same package time (psop44), the speeds are good. I generally use SD's as that's what I can get cheap.
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prj
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« Reply #2 on: May 02, 2013, 09:45:37 AM »

Hardware switching with a running ECU will leave you stranded with a checksum fault Smiley
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papasound
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« Reply #3 on: May 02, 2013, 10:53:26 AM »

I have tried to do both google site search, internal search and advanced search, nothing brought any useful results,
could you please paste links to these posts?
Software switch is ok, i think codeword can trigger different address, but i will have to always keep laptop in my car to do the switch with vagcom,
while hardware all i need is to shut down the engine do switch and go ahead.

If i'm correct all i need to do is to install switch between pin 23  - VCC +5.0 V single power supply and mainborad.
or is there anything else i should know before?
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prj
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« Reply #4 on: May 02, 2013, 11:28:55 AM »

I have tried to do both google site search, internal search and advanced search, nothing brought any useful results,
could you please paste links to these posts?
Software switch is ok, i think codeword can trigger different address, but i will have to always keep laptop in my car to do the switch with vagcom,
while hardware all i need is to shut down the engine do switch and go ahead.

If i'm correct all i need to do is to install switch between pin 23  - VCC +5.0 V single power supply and mainborad.
or is there anything else i should know before?

Easily possible to make it switchable via cruise control stalk or pedals.
Hardware switch, as I said, if ECU is running at that moment (and ignition off does not mean it's not running), you are eventually going to be stranded with the car.
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nyet
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« Reply #5 on: May 02, 2013, 11:31:46 AM »

But you could (in theory) replace a number of map lookups with hacked code to check some sort of ram location (or ECU input, or adaptation value) to decide on a map to use at run time..
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prj
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« Reply #6 on: May 02, 2013, 11:36:40 AM »

Correct, that's how it's done properly.
I do this for my meth kit failsafe.

You can also just program some code to switch with pedals and write a value to CAN instead of nmot_w, and see it on the tacho.
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papasound
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« Reply #7 on: May 02, 2013, 01:51:43 PM »

Unfortunately i'm dumb in assembler and software solution for me would introduce more problems rather than solutions.
So i'm still opting for hardware switch. It would be placed on ecu and to switch you would have to open bonnet,
so unplugging battery is 10 seconds job.

Reading the sheet now i think that one of the pins should be switchable either CE# = Chip enable or OE# = Output enable,
If someone had success with that particular chip could you enlighten us please?
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