DATA PROCESSOR

PURPOSE: To improve efficiency by making the sequence of a microinstruction for executing a machine instruction changeable according to the state of a machine, providing a control means responding to the present microinstruction and the state of the machine, and allowing a microsequencer to respond to it. CONSTITUTION: ACU 104 and a PU 106 of a computer system operate various functions of the control of the system and the execution of a program. AD bus 112 is connected as the path of information exchange between the CU 104 and the PU 106. The elements of the CU 104 are an instruction prefetch and decoder 114, microsequencer 116, memory controller 118, and system clock generator 120. Then, the PU 106 operates under the control of the microinstruction of CU 104 and executes the program of the user. That is, the PU 106 performs all the functions of data operation, calculating operation, address designating operation, and the transfer of information between a CS 101 and an outside storage element.