| 摘要 |
PURPOSE:To avoid the program memory from being read out externally, by making the erasable read only memory interrupting state independently of the state of input signal. CONSTITUTION:In the one chip microcomputer, CPU1, ROM2, RAM3, and input and output unit 4 are connected to the bus 5, and ROM2 is incorporated with the erasable read only memory EPROM. EPROMQ4 used for the control signal output circuit keeps non-conductive state independently of the state of input signal I1 when negative charge is given to the floating gate, and high level is fed to FETQ6 to keep conductive state with the operating state, low level is held at the output terminal to inhibit to read out the program memory externally. |
