Fw: Eprom switcher

[Clare Snyder]

I piggybacked two eproms, pin for pin, with the enable pins separated and
switched - this was in a small computer, not an ecu
>
>----------
>> Von: Clare Snyder <clsnyde at ibm.net>
>> An: diy_efi at coulomb.eng.ohio-state.edu
>> Betreff: Re: Eprom switcher
>> Datum: Mittwoch, 13. August 1997 14:29
>> 
>> I missed the start of this thread. What are you trying to accomplish? I
>have
>> two eproms in the disk controller of my old COCO. They are connected in
>> parallel, pin for pin, except for the enable pin, which has a simple spdt
>> switch to select which prom is being accessed. This allowed use of two
>> different operating systems, RSDOS and ADOS. I likely still have the
>diagram
>> in an old Rainbow magazine somewhere.
>> 
> Hi,
>The main problem is the space for an additional eprom in a small ECU. Some
>have a seperate shielding box inside, so i would use the gatters, flipflop
>and resistors as smd parts. It is easier to use a 27C512 eprom when only a
>27C256 is normally needed and switch from the lower half to the upper half
>(or do it with 4 sections  when a 27C128 is standard) because of the same
>ammount of pins. The additional parts are only necessary when i want to
>switch under load; that is the real comfort.
>Bye,
>Peter
>s68558 at stud-mail.uni-wuerzburg.de
>
>