PROM Switching (Was PC war thread)

[Shannen Durphey]

Frederic Breitwieser wrote:

> Hey Joe,
>
>

> There's a chip made by Dallas Semiconductor, which is an EPROM compatible
> replace chip - except its static ram, has a 10 year lithium battery, and
> about $6 instead of $1.
>
> The issue would be, writing information to the chip while the GM computer
> is reading it... which it does pretty much constantly while the ECM is
> running its code, looking up data, etc.
>
> Theoretically, it could be done, if the ECM was halted (turnd off, or put
> into "sleep" mode, much like a notebook).
>
> There is a product like this... I've seen them on the Grand National e-list
> (you know, the black high-powered turbo Buick Regal?), where you can
> install 4 EPROMS into this "black box", and select them on the fly.  This
> allows the stock chip for sunday cruises, a mild chip for street light
> games, a more radical chip for higher boost levels, and a fourth chip for
> making coffee :).  Seriously though, there are products that do this, minus
> the coffee joke.With an embedded system I made a few years back, I used the Dallas chip I
> mentioned, so I could reprogram it easily without having to pull the chip,
> go up two flights of stairs, plug it in, re-program it, then go back
> downstairs, plug it in, and find that my changes were worse.  The
> application was an alarm system, but the theory is the same.
>
> Eproms and EEPROMS have a Chip select pin, where as grounding this pin
> enables the chip.  Ground one at a time, and you can run them in parallel
> electronically, and only use one at a time.  This is how the aforementioned
> device for the turbo regals work, with some circuitry to stabalize the chip
> selection.
> There's my thoughts, I'm sure others will chime in.  So Mr Mechanical, how
> do I shove 4 valves per cyl on my Buick heads .
>
> Frederic Breitwieser
> Bridgeport, CT 06606
>
> Homebrew Automotive Website:
> http://www.xephic.dynip.com/
>
> 1993 Supercharged Lincoln Continental
> 1989 HMMWV
> 2000 Buick-Powered Mid-Engined Sports Car
>
  Hey, Fred.  I've got the small end of my cone shaped hat at my ear, so I
should be able to get everything now. : )

In a general sense, how does the chip you mentioned replace an eprom?  And how
do you program it?

I've seen those black boxes you mention.  I've seen one in a mid 80's car mag.
with 10 chip slots.  I could never understand why anyone would need that many.

Are you suggesting electronically switching from the test prom to a stock one,
?reprogram? the test prom, and switch back while the car's running?

And on a side note, have you checked out any Kenne Bell stuff?  Not that they'd
have any 4 valve heads....

Shannen