BSII and BCD thumbwheel switches (repost)

Archiver

Hi all!

This is my first post and I am a rank beginner. I've searched the
posts for an answer to my question without much luck. Any
help/websites/code is greatly appreciated.

I am using Solutions Cubed pocketwatch interfaced with a BSII. I need
to input a time in hh[noparse]:mm:[/noparse]ss fashion with the use of BCD thumbwheel
switches. I am at a loss as to how to accomplish this. More
specifically, I don't know what the output of the thumbwheel switches
are.

Forgive me if this is too simple of a question for this group, but my
mind is too so I have no choice but to ask.

Thanks in advance,

Guy Lopes

Archiver

>I am using Solutions Cubed pocketwatch interfaced with a BSII. I need
>to input a time in hh[noparse]:mm:[/noparse]ss fashion with the use of BCD thumbwheel
>switches. I am at a loss as to how to accomplish this. More
>specifically, I don't know what the output of the thumbwheel switches
>are.

I'll have a go at it. The BCD switches will eat up four bits each. BCD
(Binary Coded Decimal) is a binary representation of the decimal digits 0
through 9. The problem with your application is that you would need to deal
with 24 inputs (six digits x four bits each). Two solutions come to mind.
One way would be to use a tri-state buffer between the switches at the stamp.
You would enable each group of four in sequence to read in each switch. The
I/O cost would be 10 pins: four for the switches and 1 each for the six digits.
The other solution would be to feed the switches into a shift register and shift
in the whole thing at once. I/O cost is about 3 pins: one for data, one for
clock and one for chip select if you are sharing the clock/data lines with
other devices. I don't think that there are 24 bit shift registers. But I
don't know everything.