Eprom memory bank switching

Ecu Hardware Modifications
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Eprom memory bank switching

Postby delcowizzid » Fri Mar 20, 2009 7:26 pm

ive lost my bank switching adapter and am trying to switch between the upper and lower memory addresses on a 27C256. now i know its pin 27 opposite pin 2 on the eprom to swap addresses. now i can use 5 volts or ground if i remember right to swap from upper to lower even without pull up resistors. but do i need to remove the pin from the ecu pcb before hand or can i leave it connected to the ecu board.and is it best to use a 10k pull-up resistor resistor connected to vcc and pin 27 or does it not really matter either way.i cant find the schematic i used last time on the net.
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Re: Eprom memory bank switching

Postby VL400 » Fri Mar 20, 2009 7:39 pm

The best way is a 4k7 or 10k resistor from VCC to pin 27 (Address Line 14). Then ground the pin 27 to select the lower address range, 0x0000 to 0x4000 - in terms of ECU memory mapping thats 0x8000 to 0xC000. Leave the pin open and you will get 0x4000 to 0x7FFF (0xC000 to 0xFFFF). Remove the pin from ECU, gives you control and not the ECU of what memory to select.

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Re: Eprom memory bank switching

Postby delcowizzid » Fri Mar 20, 2009 8:23 pm

cheers mate campion answer again.will remove the pin connection then.any issues with removing the pin and switching with the engine idling if i use the same codebase for both bins.i might add up the other schematics i have for 27C512 etc later allways good info to have.


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If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem

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Re: Eprom memory bank switching

Postby delcowizzid » Sat Mar 21, 2009 1:03 am

ok to switch 4 16kb bins on the 27C512 or 27SF512 which should be the same.you need to connect a second 4.7k or 10 resistor from vcc to address pin A14 and remove the pin from the pcb and a wire to a second switch or even a rotary switch would be easier and connect both pins to it instead of 2 switches and earth it as well as the other pin now you have upto 4 combinations of both switches on or off to choose what addresses in the eprom are output as shown below.

A15 = 0, A14 = 0; 0x0000 - 0x3FFF
A15 = 0, A14 = 1; 0x4000 - 0x7FFF
A15 = 1, A14 = 0; 0x8000 - 0xBFFF
A15 = 1, A14 = 1; 0xC000 - 0xFFFF
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem

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Re: Eprom memory bank switching

Postby VL400 » Sat Mar 21, 2009 8:53 am

Nice pictures :)

If you are running the same code base there shoulc be no hiccup at all, idle or full throttle. The only difference being the calibration data and how that effects the engine. Running a different code base the engine must be off and really should disconnect battery to clear the RAM before turning the key on again.

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Re: Eprom memory bank switching

Postby delcowizzid » Sat Mar 21, 2009 9:15 am

haha yeah its hard to draw resistors in windows paint thats for sure.moved topic into hardware mods couldnt decide where it should go.since vl400 liked my pics i added another for 4 16k bins on a 27C512.
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem

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Re: Eprom memory bank switching

Postby Dec_head » Fri Dec 18, 2009 10:20 pm

I have a setup i used in a vr v8 auto switching two bins running a 27c1001 if anyone wants to try it.
But i have now gone manual has anyone got a schematic to switch 4 bins on the 27c1001

Just found this might be more helpful if using a 27c1001 for switching between mulitple bins
http://www.iroczone.com/2009/10/understanding-how-the-code-switching-eprom-circuit-works/

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Re: Eprom memory bank switching

Postby lampik » Mon Jan 16, 2017 2:11 am

im interested about how to set the bins Up i have 27c512 on my digifant ECU and i would like to know how to set all properly what pins are used to switch and what range of eprom to locate the seperated maps.

Im trying to make launch control, does anyone how to bite it ?

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