SWITCHED EPROMS

[Justin Albury]

Frederic Breitwieser wrote:
> 
> >i have found the these to work fine in the P4 and also in TECH-1
> >cartridges.  if you use the same base code and only change the data of
> 
> I liked your design, however I wish to submit the following comments.
> Instead of using SPST switches directly attached to the E/Eproms, its
> important to make them bounceless, whereby when switching, the real
> millisecend on/off/on condition assiociated with mechanical switches is
> therefor eliminated.  I have a schematic in my archive I can share, when I
> get home, not a problem.
> 
> Then, after making the switch bounceless, you use either a Flip-Flop
> circuit or four inverters to control the enable lines of the two eeproms,
> which you are correct, can only have the data set information changed, not
> the actual code.
> 
> A friend of mine who designed embedded systems for a career, has such a
> system that actually allows CODE changes... this is because, the main loop
> of the program always starts at one particular address, on both chips, then
> the processor switches the enable pins on the EEprom, not a mechanical
> switch.  The mechanical switch controls one of the inputs on the processor,
> when when it hits the beginning of the loop, where the code is the same in
> both chips, will enable or disable the appropriate eeprom.
> 
> Just some thoughts :)
> 
> Frederic Breitwieser
> Homebrew Automotive Mailing List
> Bridgeport, CT 06606
> http://www.geocities.com/MotorCity/Downs/4605/index.html
> 1989 AG Hummer 4-Door
> 1993 Supercharged Lincoln Continental
> 2000 Mid-Engine Sports Car <smile>
> 
> ---
thankyou   could you please mail me when you have a chance

Justin