| 摘要 |
PROBLEM TO BE SOLVED: To provide a write protect circuit in which a CPU smoothly starts when rebooting the CPU even when abnormal data are written in a nonvolatile memory by masking write to a bank of the nonvolatile memory where a program read when the CPU has booted is stored when the CPU runs away. SOLUTION: When the CPU starts, information about the bank of the nonvolatile memory where the newest program is stored is memorized beforehand to prevent writing abnormal data in the bank even when the CPU runs away. A bank signal and wright access from the CPU are input in an OR circuit, and by utilizing the bank signal as a gate signal, a write signal is not output when accessing the bank. COPYRIGHT: (C)2004,JPO |
