JPS6454533A - Processor - Google Patents

Abstract

PURPOSE:To decrease the number of times of the manufacture of a technical sample, and to remarkably shorten the development period, by switching and outputting a substitute program stored in a RAM so as to correspond to a program and an address, in accordance with an instruction at the time of access to a ROM. CONSTITUTION:When a part to be corrected has been generated in a microprogram stored in a ROM 5, in an address of a RAM 6 corresponding to its part, an address of a RAM 7 in which a corrected micro-instruction has been stored in written, and when an address of its part has been designated by an access to the ROM 5, the corrected micro-instruction outputted from the RAM 7 is selected by a selector 9 in accordance with an output signal 103 of the RAM 6 and sent out to an instruction unit 1. In such a way, a partial correction of the program of the ROM 5 can be executed. Also, by storing a branch instruction in the RAM 7, and storing the corrected micro-instruction in a RAM 8, a correction of only a word number portion of the RAM 7 can be executed. By the constitution which considers the capacity balance of said RAM 7 and 8, the performance deterioration is reduced and the correction quantity can be enlarged.