| 摘要 |
PURPOSE:To prevent the limitation of multiplex degree of a subroutine call regardless of the number of return address saving registers, by executing the call instruction of the subroutine after writing the microinstruction in an exit address of the subroutine by a writing means. CONSTITUTION:When a subroutine call instruction is detected in an address A during execution of a routine 1, a jumping destination address B involved by said call instruction is held by a next address register 1 by the timing T1. Here '1' is added to the reading address A of the present microinstruction by an ALU 9 and the address A is held by an increment register 10 as a return address to a routine 1. Then such a return address is written to an address part 42 of a branch instruction register 4. While the microinstruction of an entrance address B of a routine 2 is read out to a memory read register 6, and a timing address selector 7 selects an increment register 10 (address: B+1).
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