Karl Townsend wrote:

On Tue, 16 Nov 2010 00:51:02 -0500, "Michael A. Terrell"
wrote:


John wrote:

You could use a couple of the outputs and run them through a binary to
decimal converter. Two outputs would change to four outputs, four
outputs would control sixteen outputs.


A binary to decimal converter would change 4 ouputs to 10 outputs.

I don't go BCD, but I use this concept on inputs all the time. A
rorary switch with three inputs has eight detents or positions. A
rotary switch with two inputs has four positions. Or four inputs can
have 16 positions. Useful in operator panels for things like speed,
feed, jog increment, mode etc. saves a lot of inputs.

I'm not seeing this concept on outputs. I'm still going to need one
opto device per out to go from 5 volt TTL to real world 110 VAC or 24
VDC. The optos are the limiting thing, there's lots of computer
resource.


You would want to latch the data on the outputs if you multiplex it.
Old TTL ICs were made for 16 to 1 and 1 to 16 mutiplexer and
demutiplexer applications. The 74LS150 comes to mind. It looks like
the major manufaturers have dropped all the older logic ICs and only
supply some CMOS versions. Jameco might still have some wide
de/mutiplexers in stock. I prefer LS around electrical noise.


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