As you may know, any digital circuit can be either combinational or sequential. And all modern microcontroller, including lm3c, consists of circuits of both types.

A simplest example for combinational logic is just a boolean expression like B = not A. This expression does not compute value of B, but rather states that B is an inverted value of signal A. In electronics world this means that once a signal comes to input A it is immediately appear on output B.

On other hand sequential logic requires and an additional input, which moves circuit from one state to another. In microcontrollers an example of such an additional signal is a clock.