1. A microcontroller comprising: a signal processing unit; a central processing unit (CPU); and a bus coupled to the CPU and the signal processing unit, wherein the signal processing unit includes a first sequencer, a second sequencer, a first instruction memory, a first program counter, an arbitration circuit and a common arithmetic unit, wherein on receipt of a first CPU request by the CPU, the first sequencer selects a first instruction stored in the first instruction memory based on the first program counter and requests the common arithmetic unit to execute a first request based on the first instruction, wherein on receipt of a second CPU request by the CPU the second sequencer requests the common arithmetic unit to execute a second request, and wherein the arbitration circuit selects one of the first request and the second request when the first and second requests compete against each other.