Abstract: An instruction having two operands includes a field specifying the bit length of a source operand and a field specifying the bit length of data to be operated upon by the execution unit. Based on size information stored in these fields, the operand bit length is modified, which avoids need for modification of the bit length of an operand by use of a macro instruction at the time of execution of an operation based on the two operands. Consequently, the program execution speed can be improved.

Abstract: A microprocessor has a register in which attributive data corresponding to a memory to be coupled to the microprocessor is written, and a control circuit which controls address signals to be supplied to the memory in accordance with the attributive data. The attributive data is composed of range data for discriminating ranges of address data supplied to an address bus, system data indicative of addressing systems of the memories corresponding to the respective address ranges, and bit number data indicative of numbers of address bits of the memories. Thus, in a case where the memory to be accessed is of an address multiplexing systems as in a dynamic RAM, the address data of the address bus is divided into row address data and column address data, which are then supplied to the memory in time division.