EPROM Switching

["nacelp" <nacelp@bright.net>]

>From years ago, in a galaxy far far away
Grumpy

Subject: P4ECM-SWITCHING
HI ALL
A FEW WEEKS AGO I STARTED OF WITH THE TOPIC OF SWITCHING EPROM CHIPS AND
HAD A FEW REPLYS WHICH ENABLED ME TO CHANGE MY DESIGN FOR THE BETTER.
NOW FOR THOSE OF YOU WHO ARE RUNNING THE DELCO P4 (IM USING THE 808) THE
SIMPLEST WAY AND MOST EFFECTIVE IS :
OH YEH THE ORIGNAL EPROM IS A 27C128, THIS IS REPLACED WITH A 27C256

1 - PROGRAM THE EPROM CHIP, THE FIRST FILE LAYS AT 00000 - 03FFF
    AND THE SECOND AT 04000 - 07FFF

2 - MOUNT IT IN THE MEMCAL (IF YOU MOUNT A SOCKET FLUSH THEN POP THE
    NEW EPROM IN YOU CAN STILL GET THE MEMCAL LID BACK ON)

3 - STICK IT BACK INTO THE ECM (THE MEMCAL THAT IS)

4 - PICK UP A 12+ POWER FEED FROM THE IGNITION, RUN IT THROUGH A SWITCH
    MOUNTED ON THE DASH/CONSOLE, THEN TO PIN C9 AT THE ECM

5 - SIMPLE .... WHEN 12+ IS APPLYED THE EPROM AT PIN 27 (A14) IS    
SWITCHED HIGH BY THE ECM AND WHEN POWER IS TAKEN AWAY THE ECM 
    SWITCHED THE EPROM LOW.

6 - I LIKE THE K.I.S.S. METHOD!
GM HOLDEN HAVE BEEN USING THIS METHOD SINCE 1991 ON LPG SYSTEMS SO WHY
NOT USE IT IN ANY WAY WE CAN.
OH YEH ITS BEST TO KEEP THE SAME BASE PROGRAM AND ONLY CHANGE THE DATA
BETWEEN EACH FILE....



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