Designing a sequential circuit using JK flip flops

[Ramir]

Homework Statement

Design [/B]:2-bit count-down counter; with two flip-flops and one input

Homework Equations

When input = 0, the state of the flip-flops does not change.
When input = 1, the state is 11, 10, 01,11, and repeat.

The Attempt at a Solution

Start with truth table, then characteristic table, and then excitation table, then Kmap?
How do I start deriving the truth table

 

[Svein]

How do I start deriving the truth table

The truth table is meaningless here. You need to create a state diagram (for example: [state 0, output 00, state change: On clock transition, next state:...]).