| 摘要 |
PURPOSE:To surely hold the secret of information without damaging the debugging function of information by prohibiting that the information read from a reading circuit is outputted to an external terminal when logical information is a prescribed value. CONSTITUTION:While the information is written in an EPROM 1 by a first writing prohibiting circuit 39, it is prohibited that the logical information is written in a memory element, and therefore, after the information is written, the logical information is read by a reading control circuit 47 and debugging, etc., can be executed. By a second writing prohibiting circuit 42, while the logical information by written in the memory element, it is prohibited that the information is written in the EPROM 1, and therefore, the information is written without destructing data. As the result, when the logical information read out of a reading control circuit 47 is the prescribed value, it is prohibited by an output control circuit 48 that the information read out of a reading circuit 3 is outputted to an external terminal 50. Thus, without removing the debugging function, the secret of the information is surely held. |
