How to design a synchronous decimal countdown timer using flip-flops

[ashleyd]

The counter must have a reset input that immediately resets the input to decimal value 10 when it is activated. If the reset is not activated, the counter should count down through the sequence 10,9,8,7,6,5,4,3,2,1,0 and it is not specified what happens the next clock pulse after the counter has reached 0
Decimal digits need to be displayed on two seven-segment LEDs
This will be created on Logisim

 

[duffy]

The part you are looking for is called a "Set and Reset J-K Flipflop". This will give you the necessary Set and Reset pins (to load a "10"), and the synchronous clock.

A 74HC109 is one version.