| 摘要 |
PURPOSE:To suppress the amount of program from being increased, by designating a return condition from a subroutine of a microprogram at a main routine for eliminating the need for a return instruction. CONSTITUTION:A micro mu instruction of an address designated at a readout address register 2 is read out in a mu instruction register 3 from a control storage 1 and decoded. When the result of decoding is a return condition set instruction from the subroutine SR, the return condition included in the mu instruction is set to a register 4, and when the result of decoding is a return condition number of detection set instruction from the SR, the return condition number of detection of the mu instruction is set to a register 5 respectively. Further, when the result of decoding is the SR call instruction, the address of the next executing mu instruction added 9 with the content of the register 2 is stored in a register 10. When the registers 4, 5 are set, the mu instruction of the register 3 is compared 6 with the content of the register 4, and when they are coincident, the content of the register 5 is subtracted 7 by 1. When the result of subtraction reaches 0, a discriminator 8 outputs a ''1'' level signal to a selector 11, which selects a register 10 as a return address. |
