MOTM

--- In motm@y..., "J. Larry Hendry" <jlarryh@i...> wrote:
> ----- Original Message -----
> From: <ixqy@a...>
> 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

I was thinking about this also.

In the bad old days, when you wanted to add more memory to 
your PAIA programable rhythm box, you just stacked the chips on 
top on one another and soldered all the pins except "chip select" 
to which you routed a flying lead to a switch. This would also 
work for the A & B sockets on the Mini-Wave, upping the wave 
count to 1024.

BUT, since the first word in analog is "anal", a more elegant 
solution is desirable %^}

The LM3914 chip can be used for logic functions if viewed as a 
set of open collector outputs. In "dot" mode, only the selected 
stage goes low, and by coincidence the EPROM chip select is 
low active. So a LM3914 powered from +5 volts with 10K pullup 
resistor to +5 volts, could allow voltage controlled enabling of up 
to 10 wavetables chips of 256 waves. Or 2560 waves, which 
would keep Mark Pulver busy for a while.

As a bonus you can probably finagle an LED on each stage to 
show which chip is selected, since the enable pin should just 
need to be pulled down below 1.4 volts?

An TL072, LM3914 and pot, would be cheaper than a 10 position 
selector switch and give external 0-5 volt control as a bonus.

Best Regards,

Grant Richter
Wiard Synthesizer