INSTRUCTION FETCHING SYSTEM

摘要

PURPOSE:To improve a processing speed by executing macro-instruction fetching processing in accordance with the validity/invalidity of a flag indicating whether a macro-instruction effective for an instruction buffer exists or not at the time of generating a microinstruction for fetching the macro-instruction. CONSTITUTION:The titled system is provided with a register 11 for counting up a macro-instruction address every '+1' in order to prepare the succeeding macro-instruction at the time of ending one macro-instruction processing, a flag forming part 12 for forming a flag 6 indicating whether the contents of the instruction buffer 7 are valid or invalid and deciding whether a main storage device 2 is to be accessed by hardware in accordance with the contents of the flag 6 and an AND 13 for finding out an AND condition between an invert signal of the flag 6 generated by the flag forming part 12 and the ON output of a register 6 in which the macro-instruction is set up and sending a memory request signal 2. Consequently, load to farmware can be reduced with simple hardware constitution and its processing can be speed up.