Method of protecting the flow of a program running in a data processing system

摘要

The way in which limitation of the protection time in programs which are to be protected from interrupts, independently of the insertion of a command sequence to switch off the protection time, is achieved, is firstly that a compiler recognises the absence of this command sequence when compiling the program to be protected, reserves a value for a counter state (Z), and that the program, when passing through a specific load command, places the counter state (Z) in a control unit (ST), and secondly that the counter state (Z) in the control unit (ST) is set by a transfer command of a central processor (ZP), or by a specific load command of the control unit (ST). Program or time events in the program to be protected increment the counter state (Z), and the protection time ends when the counter state (Z) equals a comparison value (R). The invention is used in data processing. <IMAGE>