The CD4026 is a 5-stage Johnson decade counter with decoded 7-segment display outputs and display enable. With RESET and CLOCK INHIBIT low, and DISPLAY ENABLE IN high, the 7-segment display outputs progress through the 0-9 sequence on the rising edge of the CLOCK pulse.
It's an interesting alternative to a shift register for driving a 7-segment LED (as in the ShiftDrive project). While a latched shift register provides random addressing and clean transitions to any digit, it requires the 7-segment display outputs to be decoded externally (like in code). On the other hand, the CD4026 takes care of the decoding, and external circuits just need to send a counter pulse.
As always, all notes, schematics and code are in the Little Arduino Projects repo on GitHub.
