| 摘要 |
A single-chip microcomputer includes a program ROM storing a program; a central processing unit executing the program read out from the program ROM for performing data processing; an external data input port for receiving data to be processed by the central processing unit, from an external device; and an external data output port for outputting data processed by the central processing unit to an external device. The program ROM also stores a test program for testing the program ROM and a plurality of bytes of collation information. The central processing unit has a test mode for executing the test program, and compares the plurality of bytes of collation information with a corresponding number of bytes of data sequentially input through the external input port. The central processing unit selects one of the plurality of bytes of collation information and compares the selected byte of collation information with one byte of data input through the external input port when the selected byte of collation information is selected. Only when the plurality of bytes of collation information are consistent with all the bytes of data sequentially inputted through the external input port will the central processing unit allow contents stored in the program ROM to be output through the external output port.
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