Help with ring counter

[jb885]

I have the following Ring Counter. In the beginning the four flip flops will be 0000 and I want after the first cycle to be 1000, then 0100, then 0010, then 0001. How can I induce that initial 1 in the beginning in a way such that it will not affect the cycles that will follow?( I mean after 4 cycles the input to be that output of the last flip flop and not the 1 from the logic I used in the very beginning). I cannot use preset/reset button.

Thanks

 

[ronsimpson]

Assume all FF are powered up in state 0.

Option1)
Place a inverter on the D of the first FF and a inverter on the Q of the first FF. The two inverters cause the data to pass through with out inversion. This makes the counter to power up in what looks like 1000. This is a common way to get a FF to power up in a 1.

Option2)
Ahead of the D of FF1 add this logic.
If Q4=1 or If Q1,2,3,4=0000 then D=1 else D=0
another way to say that is: D=Q4 OR /(Q1+Q2+Q3+Q4)

 

[jb885]

Many thanks!

 

[ljcox]

The logic can be simplified to

D = Q!'.Q2'.Q3' where Q!' means the complement of Q!.

Hint, use a 3 input NOR gate.