| 摘要 |
<p>PURPOSE:To protect a memory by normally setting a read/write changeover switch circuit to the read mode to prevent erroneous write even for runaway or the like of a CPU. CONSTITUTION:In case of write, a CPU 2 outputs excitation output data 11A to a changeover switch control circuit 11 to excite an exciting coil 11B for an changeover switch, and a read/write changeover switch 10A of a read/write changeover switch circuit 10 is switched to the write mode. An address is designated by an address bus 4 after confirming setting of the write mode by a changeover switch state monitor circuit 12, and new data is written in a memory 3 in accordance with the address by a data bus 5. After such writing, the output of excitation output data 11A is stopped to set the read/write changeover switch 10A to the read mode again, and write completion is confirmed.</p> |
