| 摘要 |
PURPOSE:To keep the secrecy of a program built in an integrated circuit IC by comparing the input signal of a program memory built in the IC with that received from the outside within the IC and outputting the result of this comparison to the outside. CONSTITUTION:A ROM 11 is actuated and the output of the ROM 11 is sent to a transmission line 16 when the contents of a program area checked. Here a terminal 17 is controlled to prevent outputs of signals to the line 16 and functions as a terminal for input of external signals. A program inspector supplies the signals expected as the contents of the ROM 11 to the terminal 17 and this signal is compared with the output signal of the ROM 11 put on the line 16 through a comparator 18. Then the coincident or dissident result of both signals is outputted to an output terminal 19. Here an expected signal can be produced and supplied from the outside as long as the contents of the program are previously known. While it is not possible to know easily the programs contents if they are not known previously. |
