| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the need for a dedicated measuring instrument by accessing a specific address of a 2nd nonvolatile memory when a one-chip microcomputer is initialized. SOLUTION: When the one-chip microcomputer is initialized, a flag 18 is reset to '0' with an initial signal TNT and the chip-enable terminal CE of a mask ROM 2 is held at '0' to place the mask ROM 2 in a readable state. When the contents of an accumulator 10 are not '00'H, the flag 18 is set with the logical output of an arithmetic logic unit 13. Then, an EEPROM (1st nonvolatile memory) 1 is enabled and the mask ROM (2nd nonvolatile memory) 2 is disabled. Further, when data in the EEPROM 1 are rewritten, a switching control signal becomes '1' according to a program instruction in the mask ROM 2 to enable both the mask ROM 2 and EEPROM 1. |
