A memory-built-in data processor comprises a controller connected to an external unit and a memory via first and second buses, and a data processor performing readout/write-in of data with respect to the memory via a third bus, the controller and the second bus, the controller performing arbitration between a first access requirement input via the first bus and a second access requirement input from the data processing unit via the third bus, the memory, the first bus, the second bus, the third bus, the controller, and the data processor being integrated in an integrated circuit.