How do I chain multiple decade counters together?

Question

On the IC CD4017 how do I use the carry out to chain multiple of them together?

I want to chain it so I would have twenty outputs of which only one is energized at a time.

Answer 1

Do you want to chain them together so you get, say, twenty outputs of which only one is energised at a time? Or to have one output energised on the "units" counter (which increments with every input pulse) and one on the "tens" counter (which increments after every tenth input pulse)?

(* edit *)
The bad news: there is no "output inhibit" line on a 4017, so you will have to add an AND gate onto each output. Use two counters and feed the "carry out" from the "units" counter into the input of the "tens" counter. Now each of your 20 outputs is made by ANDing a "units" output with the appropriate "tens" outputs. As you're using 20 outputs, you can take your "reset" signal from the "2" output on the "tens" counter.

Alternatively, look at the block diagram in the 4017/4022 data sheet (linked below) and build yourself a Johnson counter using 10 flip-flops instead of 5 or 4. This might actually work out easier. (If you draw a full truth table, you will see that each output needs only a two-input AND gate. Also note that an AND gate with an inverter on each input, as it's been drawn in the data sheet, is equivalent to a NOR gate.)

Answer 2

Highest o/p of chip one to input of chip 2.