[Diy_efi] Looking for help with a prom N82S181

Ludis Langens ludis at cruzers.com
Mon Nov 8 09:38:43 GMT 2004

mbelloli at speedymotorsports.com wrote:
> Hello Everyone,
>      I am in the middle of changing the spark table for a friends 1984 gmc
> pickup with computer controlled timing, and carburetor.  I've done
> quite a bit with the tbi ecms, and honestly this is my first computer
> of this generation.  I have been able to copy the prom, and with help
> found the spark table.  I've modified it, and put a copy of it on a
> 2716, which is a 2k x 8 eprom.  I started with a N82S181 1k x 8 prom.
>  I thought I would be able to just simply drop the eprom where the
> prom was, but I wasn't so lucky.  I am not familar with the chip
> enable on the original chip, N82S181.  It has 4 chip enable lines,
> and it looks like two of them are hex inverted.  Does anybody have
> any idea how this chip works???  I got a data sheet from Jameco,
> which helped but was missing key information.  I figure I'm going to
> have to make a dip socket sandwich with some changes for the enable
> logic.  Thanks,  Marcello A. Belloli

Look here http://www.cruzers.com/~ludis/c3pinouts.html for the pinout
data.  You'll have to figure out which chip enable GM is using (and hope
that they are only using one of them).  The ECM likely has a 74138 type
decoder for the chip selects, so you are probably OK.

Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
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