Data processing system with improved microsubroutine facility

Claim 1

A data processing system having an improved microsubroutine facility comprising: first storage means for storing therein macro instructions; means including a program counter coupled to said first storage means for supplying an address of a macro instruction next ot be executed to said first storage means; second storage means for storing therein micro-programs for executing said macro instructions; means including an address register coupled to said second storage means for supplying an instruction address of a microprogram next to be executed to said second storage means; stack means for storing therein a return address of the microprogram; first means responsive to a first microinstruction, which instructs a microsubroutine call, for storing the return address of the microinstruction in said stack means, and responsive to a second microinstruction, which instructs a return from the microsubroutine, for returning the return address of the microinstruction from said stack means; mode indication means for indicating whether the execution mode of said macro instruction is a control program mode or an application program mode; means including a status register for indicating the operation status of a macro instruction being executed; interrupt control means for monitirong an interrupt request; second means for determining acceptance or non-acceptance of the interrupt request on the basis of said mode indication means including means for setting into said address register a microinstruction address for executing the macro instruction specified by said program counter, when an interrupt request is not accepted, and for storing the contends of said status register, the indication of the program mode, and the contents of said program counter, when the interrupt request is accepted, and means for setting pattern information which corresponds to the execution mode after the interrupt into said status register and said program counter and thereafter setting the microinstruction address specified by said program counter into said address register, thereby restoring the information stored at the time of an interrupt to said status register and said program counter; third storage means for storing therein the contends of said stack means; means including a halfway interrupt indicating field for indicating that an interrupt request was accepted in the course of the execution of a macro instruction; and third means responsive to an interrupt request detection signal from said interrupt control circuit for setting the halfway interrupt indicating field to an interrupt indicating state, when an interrupt request is accepted, and for saving the contents of said stack means, the contents of said status register, the indication of the program mode, and the contents of said program counter, in the course of the execution of the application program mode, and means for setting said halfway interrupt indicating field to a non-interrupt indicating state and for restoring the contends of said stack means after completion of the execution of the interrupt program.