74190 chip question

[jpd]

Hello. I have to do a proyect for the university. I need to make a counter that goes like this. 0 1 2 3 4 5 6 7 8 9 8 7 6 5 4 3 2 1 0 1 2... I alredy mounted the circuit but I don't now how to make it count back when it reaches 9. I did it with an interruptor but the idea is that it work automatically. Anyone knows how to do it?

 

[JimB]

Anyone knows how to do it?

My first thought is to build some logic which can detect when the counter output is "9", the logic will then set the up/down input of the 74190 to DOWN.
Also, have some logic which detects when the counter output is "0", that logic will then set the up/down input of the 74190 to UP.

JimB