| 摘要 |
<p>PURPOSE:To prevent a CPU from running away and to reduce the malfunction of a system by providing a microcomputer with a runaway monitoring circuit. CONSTITUTION:There are two cases for outputting a reset signal 11 from the runaway monitoring circuit 5 to the CPU 1. When a ROM chip select signal 13 is non-active, a memory read signal 8 is active and a CPU status signal 10 is in an operation code fetching cycle in the 1st case, the CPU 1 is reset if addresses are not in a ROM area though the CPU 1 is in the operation code fetching cycle. If the CPU 1 tries to write data in the ROM 4 when both of the ROM chip select signal 13 and memory write signal 8 are active in the 2nd case, the CPU 11 is reset. Consequently, the system can be prevented from generating malfunction.</p> |
