1. A microcontroller comprising: a signal processing unit; a central processing unit (CPU) that sends a plurality of commands to the signal processing unit; and a bus coupled to the CPU and the signal processing unit, wherein the signal processing unit includes a first sequencer, a second sequencer, an arbitration circuit and a common arithmetic unit, wherein the first sequencer requests the common arithmetic unit to execute a first request among the plurality of commands, wherein the second sequencer requests the common arithmetic unit to execute a second request among the plurality of commands, 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.