How to use a MUX DEMUX to communicate two circuits?
As long as you allow ground as an uncounted line, you can do it a bit more simply than Asmyldof suggests. Not only that, you can do it for as many channels as you like.







simulate this circuit &ndash; Schematic created using CircuitLab

The counters are synchronous reset, and the carry is active when the counter is at max carry. The polarities of the carry and reset must be the same. 74HC163 is a type IC, except that the carry and reset are of opposite polarities, so an inverter must be used.

There are only 3 signals required: clock, reset and data.

The counter size can be more or less indefinitely extended.