In a project, i have a clock-signal and two other signals (A and B). A and B are the opposite of each other - when A is HI, B is LO, and vice versa. This project has no microcontroller (or similiar) involved, I have to solve it using basic logic components (gates/diodes, TTL/DTL, etc).

Here's the problem:

I want signal A to depend on the clock. At each edge-fall of the clock, A should change it's state. I.e., when clock goes from LO->HI, nothing happens. When clock goes from HI->LO, A goes from HI->LO or LO->HI, depending on its current value.

The value of B is the inverted value of A, so there's no headache for me there, but since I haven't worked with signal transitions before I cannot seem to find a way for signal A to depend on the clock as described.

I'm pretty much clueless and I'd be grateful for any hints of how I might find a way to solve this trickster.