| 摘要 |
PURPOSE:To curtail the number of steps of a microprogram by supplying an entry address of a micro-subroutine from a mapping address register, and eliminating a delay in case of a branch of the micro-subroutine. CONSTITUTION:An instruction of an instruction register 1 is decoded by a mapping array MA 2, an address corresponding to its instruction is outputted to a mapping address register MAR 3, and by a selector 103, its address is selected and supplied to a control storage CM 5. Subsequently, the selector 103 selects an output of a counter 7, an address is added by '1' successively, and a microprogram is executed. A branch to a micro-subroutine is executed by saving an output of the counter 7 into a return address register 101, suspending the microprogram which has been brought to mapping for the first time, and selecting a mapping address of the second time, namely, the head address of the micro-subroutine.
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