Rumor has it that ajp166 may have mentioned these words:
>>> > I've never seen SPDT dipswitches in computers.
>
>
>I have some. Also I have some S100 boards that used them for address
>selection.
>
>Allison
And that's what I want them for. With Tony's advice, I figured out a way to
design my board with (2) separate CE/ signals (Is that how you denote Chip
Enable, Active Low in ASCII?) but I needed a variable way to address from 1
to 4 memory locations to each CE/ externally -- that's why I don't want to
monkey with a chip-based solution -- switches are just easier that way when
tinkering.
My idea: A 2-4 decoder/demux. tied to A0 & A1, with the outputs going to
one side of a SPDT DIP switch, the other side of the switch pulled to +5,
then all four of the switch outputs going into a 4-input AND gate. That
way, you could switch any of the four addresses on or off, so that you'd
have access to more than one memory location for CE/ to implement UARTS &
stuff that require more than one address to function. (It can be done
easily without the switches -- I could use a jumper block without
heartburn, but the switches would look neater, and wouldn't have the chance
for floating inputs/outputs...)
Dunno if it make sense to y'all, but it looks good (so far) in my head,
anyway... ;-)
Anyway, that's my plans -- now back to AutoCad to start mapping the stuff
in. Hopefully I'll have an updated board uploaded to the website by next
weekend... :-)
Laterz,
"Merch"
P.S. Thanks everyone for the helpful tips on where I might locate these --
I'll start hitting the web & phone next Monday to attempt to fine a
supplier. (I have a clutch to fix on an '84 Pontiac Fiero that I fear will
take a large portion of my weekend... :-(
--
Roger "Merch" Merchberger --- sysadmin, Iceberg Computers
Recycling is good, right??? Ok, so I'll recycle an old .sig.
If at first you don't succeed, nuclear warhead
disarmament should *not* be your first career choice.
Received on Sat Sep 15 2001 - 13:42:15 BST