DATA PROCESSOR

PURPOSE:To eliminate the overhead of a command transfer to a co-processor and to improve the execution performance of a co-processor and command by decoding a command even in the co-processor at the same time as the command decoding of the pipeline processing of an MPU. CONSTITUTION:A co-processor 200 is composed of a command decoder 230 and a co-processor command executing circuit 240, the command decoder 230 receives the command to execute the decoding from a command register 120 of a microprocessor (MPU) 100 through the use of an exclusive-use command transfer bus 250, and when a command decoding start instructing signal 180 is asserted, the decoder 230 decodes the command. As a result, when the command is the command to be executed by the co-processor 200, a decoded result is sent to the co-processor command executing circuit 240, and a processing according to the command is executed. Thus, the overhead can be eliminated, and the processing performance of the co-processor 200 can be improved.