Facilitating return from an on-line debugging program to a target program breakpoint

Claim 1

In an instruction executing computer system having memory means for storing information including a target program of instructions and a debugging program of instructions, a trap instruction having been inserted at a breakpoint location in said target program in place of one word of a selected instruction thereof to transfer control therefrom to said debugging program, said one word and its original address in said target program having been stored elsewhere in said memory means, and said debugging program including a return instruction; an arrangement for returning control of said system from said debugging program to said target program comprising: a plurality of registers; sequence control means coupled to the one of said registers containing an instruction to be executed for selectivey generating a sequence of control signals to control the performance of the set of functions defined by said instruction to be executed; program counter means coupled to said memory means for specifying the location in said memory means from which said information is to be retrieved; retrieval means connected between said memory means and some of said registers, including said one of said registers, and operative in response to certain of said control signals generated by said sequence control means for transferring said information from said location in said memory means sepcified by said program counter means to at least said one of said registers; and gating path means intercoupling said plurality of registers and said program counter means and operative in response to others of said control signals for selectively transferring the contents of said plurality of registers among them and to said program counter means; said sequence control means first operating in response to completion of the performance of the preceding said set of functions, including transfer of said return instruction to said one of said registers, to generate a first sequence of control signals to control performance of the particular set of functions defined by said return instruction, said particular set of functions including operation of said retrieval means and said gating path means to transfer said original address to said program counter means from said memory means and to transfer said one word to said one of said registers from said memory means, and thereafter operating in response to said first sequence of control signals, without first transferring any information from said memory means, to immediately generate a second sequence of control signals to control performance of the set of functions defined by said selected instruction.

Claim 6

The method of returning control of a computer system to a program wherein one word of a selected multi-word instruction in said program has been replaced with a transfer instruction, said one word and its original address having been saved in memory means of said system; the method comprising the following steps: 1. retrieving said one word and its original address from said memory means and storing them, respectively, in the instruction register and program counter of said computer system, and 2. without further retrieval of information from said memory means, immediately initiating execution of said selected instruction.

Claim 7

The method of returning control of a computer system to a program wherein one word of a selected multi-word instruction in said program has been replaced with a transfer instruction, said one word and its original address having been saved in memory means of said system; the method comprising the following steps: 1. retrieving said one word and its original address from said memory means and storing them, respectively, in the instruction register and program counter of said computer system, and 2. without further retrieval of information from said memory means, immediately initiating execution of said selected instruction.

Claim 8

The method of returning control of a computer system from a testing program stored in memory means of said computer system to a target program also stored in said memory means and in which a single word breakpoint trap instruction has been inserted in place of the first word of another instruction of said target program, said replaced first word of said other instruction and the address of said breakpoint trap instruction having been stored elsewhere in said memory means; the method comprising the following steps: 1. retrieving said replaced first word of said other instruction and said address of said breakpoint trap instruction from said memory means and storing them, respectively, in instruction register means and program counter means of said computer system, and 2. without further retrieval of information from said memory means, immediately initiating execution of said other instruction.

Claim 9

The method of returning control of a computer system from a testing program stored in memory means of said computer system to a target program also stored in said memory means and in which a single word breakpoint trap instruction has been inserted in place of the first word of another instruction of said target program, said replaced first word of said other instruction and the address of said breakpoint trap instruction having been stored elsewhere in said memory means; the method comprising the following steps: 1. retrieving said replaced first word of said other instruction and said address of said breakpoint trap instruction from said memory means and storing them, respectively, in instruction register means and program counter means of said computer system, and 2. without further retrieval of information from said memory means, immediately initiating execution of said other instruction.