| 摘要 |
PURPOSE:To protect software, by providing an internal program ROM to a one- chip microcomputer, and inhibiting the 3rd party other than a specific person from reading the program ROM. CONSTITUTION:The internal program ROM9 of the CPU1 is stored with an optionally specified key code and a comparative decision program. An external signal is received and the key code and decision program are compared; only when coincidence is obtained, a specific instruction word is generated to set a specific flag. When not, the execution of the program ends. A control signal for indicating whether an external read of the ROM9 is made or not is generated according to the logical combination of the set/reset signal of the flag and an external input specifying signal. Thus, the key code is inputted by the program execution to set the flag and then a read of the internal ROM is allowed. |
