At 11:43 PM 8/20/97 -0800, you wrote:
>Mike <PICLIST@MITVMA.MIT.EDU> wrote:
>
>> WHy not treat the thumbwheels as if they are keys annd use diodes,
>> selecting the group via one of three port pins -  Ah la HC139 etc ?
>
>Mike:
>
>That's the "seven pins and twelve diodes" method that was mentioned
>in the original question.  The diodes are necessary because ALL
>combinations (from no sitches closed all the way up to all 12
>switches closed) need to be unambiguously read.

Yes Andy but, thats 6 pins. I think I prefer the dual HC165 method
instead since its only 3 pins - yet 16 bits of input, no diodes and
only a couple of cheap 100K SIPs...

Rgds

Mike
perth, Western Australia