| 摘要 |
PURPOSE:To detect a program stole at low cost by resetting a time measuring instrument by the program of a controller at intervals within prescribed time, and by sending an interruption signal to the controller when the instrument is not reset for longer than the prescribed time. CONSTITUTION:According to a program stored in a memory part 4, a CPU1 controls various input and output equipments, and sets the time, obtained by adding something to the longest time among the execution times of tasks, to a time counter 3 as a count value, starting time counting operation. The counter 3 counts a fundamental clock from a clock generator 5 and when the execution of each tank is completed during said period, the CPU1 sends a resetting indication to the counter 3. Each time the resetting indication is sent, the counter 3 restarts counting from its count initial value and when its reaches the set count value, a count end signal is sent to an interruption controlling circuit 2, which sends an interruption signal to the CPU1. Consequently, the CPU1 discriminates a program stole and the program being executed is interrupted and a program stored at and after interruption-specified addresses is executed. |
