| 摘要 |
PURPOSE:To protect internal data by forming a programmable non-volatile memory and storing data for inhibiting a test mode of a one-chip microcomputer at least in one bit of the non-volatile memory. CONSTITUTION:After executing an internal test in a test mode, specific data are written in specific two bits of the non-volatile memory 8 from the external in the test mode state, and at the time of ending the writing, two bit data '1' are outputted from the memory 8 and inputted to a decoder 9. When the two '1' data are combined so that the output of the decoder 9 is '0', the output of the decoder 9 is turned to '0' and inputted to an AND circuit 10, so that even if a test input is 'H', '0' is inputted to a test circuit 7. Namely, the 2-bit data becomes data for inhibiting the test mode and the test mode is inhibited. Since the memory 8 is a non-volatile memory, data written once are not erased at the time of non-use of the microcomputer and the inhibition mode is maintained. |
