Fw: Eprom switcher

[Peter Rueb]

----------
> 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