GB1480520A - Electronic computer with debugging equipment - Google Patents

Abstract

1480520 Computer ING C OLIVETTI & C SpA 13 Dec 1974 [28 Dec 1973] 53991/74 Heading G4A A computer has a switching element operable to define two modes of operation in which normal and debugging programs respectively are executed. The computer is a microprogram-controlled device having a read/write store for program instructions and data and a read-only microprogram store. When the switching element, e.g. a key or switch, is set to "debug" the current programm is interrupted, status data being saved in a reserved area of the read/write store to enable a subsequent return, and the debugging programs, which may be stored in the ROM, are accessed. The first part of the debugging program saves further status data and visually displays the relative address of the current instruction of the interrupted program and the instruction itself, the address being relative to a base stored in a store register and being calculated by subtracting the base from the current absolute instruction address. The program continues by sensing which of several keys on the keyboard have been actuated to select the debugging program to be executed. The debugging programs include programs arranged to display the instruction following that already displayed, to display the instruction stored at an address entered on the keyboard, to cause a normal program subsequently run on the computer to halt at the instruction whose address is entered on the keyboard, to replace the instruction currently being displayed by an instruction entered on the keyboard to allow instructions to be corrected, and to execute the next instruction to allow step-by step execution of a program under test. If debugging programs other than those stored in the ROM are required it is possible to enter a debugging program read from a magnetic card or tape &c. into the read/write memory from where it is executed under microprogram control. Each program so executed is arranged to reactivate the previously interrupted program, to activate a further debugging program, or to actuate a further program read from the magnetic cards. To avoid having to provide more read/write storage than is necessary for normal programs provision is made to enable part of the contents of the read/write store to be transferred to an external store, e.g. a magnetic disc, and to use the space vacated to store a debugging program.