MOTM

----- Original Message -----
From: <ixqy@...>
Hi Larry and list,
I was thinking about something like this earlier today (well, yesterday
now). It'd be nice to have an "aid" module with the space for lots and lots
of ROMs, all immediately accessible via a couple of switches. I have two
Miniwaves, so maybe an aid module could even select individual ROMs and
route them to different Miniwaves?

--LH--
Well, switching a from one ROM to another in the same Miniwave module is an
easy affair as I see it.  However, switching one ROM between 2 Miniwave
modules is a whole different ball game.

Unless I am missing something, all the ROMs are wired in parallel except for
one pin.  Switching pin 20 from ground to 5 volts appears to enable or
disable the ROM.  Now, I admit to knowing nothing about the PROM.  But, it
seems it would be simple enough to have a single pole, 10 position, digital
(not BCD) thumbwheel selector switch with 10 positions numbered 0-9 to
replace the A / B switch on the front panel (I've been checking out some).

A separate PCB could be constructed to with sockets for 9 chips.  It would
have a ribbon cable of some nature that would plug into the socket in the B
position of the Blacet Miniwave (except leave out pin 20).  No need to
modify the Miniwave.

It looks to me  like grounding pin 20 enables the ROM and putting 5 volts on
it disables it.  So, the common connection point on the 10 position switch
would connect to ground at point 3 on the PCB replacing S1.  The 0 position
would connect to SW1 point 2 to select the on board ROM, and positions 1
through 9 would go to the new PCB to select those sockets.  Looks like  we
could pick up 5 volts at the now unused R27 position and have 9 100K
resistors on the new PCB (one for each pin 22 just as John has the "B" chip
wired now).  But, I could have that backwards.

I might be making it too simple.  But, I don't think so.  What about it
John?  See any problems?  Is my thinking screwed up?

Yes, you could have a separate module with a rotary switch or something.
But, I was thinking of something that could use
the existing panel and basically replace the BANK A/B box.  But, cutting the
square hole would sure be a bitch.

Larry (also thinking out loud)