| 摘要 |
PURPOSE:To prevent data which are stored in a ROM from being read by controlling whether the data of the ROM are outputted or not according to coincidence between data which are inputted from an external part when a power source is inputted, and data to be read from the ROM just after a test condition is obtained. CONSTITUTION:A microcomputer has an input data latch circuit 4 to latch input data when the power source is inputted, a ROM data latch circuit 2 just after the test condition is obtained, a coincidence detecting circuit 3 to detect the coincidence between the output of the input data latch circuit 4 and the output of the ROM data latch circuit 2 and a control circuit 6 to control whether the ROM data are outputted or not according to the coincidence to be detected by the coincidence detecting circuit 3. Thus, even when the test condition is obtained, the data stored in a ROM1 are not outputted to an external part and the data stored in the ROM1 can be protected to any person excepting a data preparing person. |
