MICROPROCESSOR

PROBLEM TO BE SOLVED: To provide a microprocessor adapted to decode the same instruction codes as each instruction for processing data of various data length. SOLUTION: In this microprocessor, a decode part includes a data length holding circuit holding data length selecting information. An instruction for specifying the data length of data stored in a general register such as an instruction for storing 8-bit immediate data in a register R1 is preliminarily determined as a first-class instruction, and an instruction for processing data stored in the general register which is an instruction without clearly specifying data length or capable of processing data of various data lengths is preliminarily determined as a second-class instructions. The decode part updates the data length selecting information according to the first-class instruction at the time of decoding the first-class instruction, and specifies, at the time of decoding the second-class instruction, the data length by referring to the data length selecting information. COPYRIGHT: (C)2007,JPO&INPIT