does the 4026 have a countdown function? it is the most commonly used ic for counters with 7 segment display, but i dont know if it can do the countdown. is there an alternative ic with similar function but instead of counting up e.g. 0 to 9, it counts down 9 to 0. i wish to connect it to the 1 hz 555 timer clock input, so i'll have a 7 segment display counting down from 9 to 0, then resets to 9 then count to zero again.

 

No... but you can use a separate up/down counter (like a cd4510) to drive a bcd-to-7segment decoder driver

 

does the 4026 have a countdown function? it is the most commonly used ic for counters with 7 segment display, but i dont know if it can do the countdown. is there an alternative ic with similar function but instead of counting up e.g. 0 to 9, it counts down 9 to 0. i wish to connect it to the 1 hz 555 timer clock input, so i'll have a 7 segment display counting down from 9 to 0, then resets to 9 then count to zero again.

CD40110 is an up / down counter with 7 segment output.

 

You can read the segment outputs with a microcontroller and output the segments for the 9's complement. Same two packages as the solution above.