| 摘要 |
PURPOSE:To prevent easily the deleting of the important data stored already by other data by connecting an AND circuit to be able to write only the important data, to a RAM for the important data. CONSTITUTION:An AND circuit 8 has a function as a write signal control circuit, and inputs the write signal to a RAM 4 for the important data in accordance with the input condition to three input terminals. Namely, only when an enable signal from a decoder 5 and the write signal and a port signal from a CPU 1 are simultaneously inputted, a controlled regular write signal is inputted to 'the inverse of WR' terminal of the RAM 4. At such a case, three signals inputted to the circuit 8, when the AND is established, are inputted to the RAM 4 for important data as the regular write signal, and the important data are rewritten. Thus, it is eliminated to input the write signal to the RAM 4 by mistake, and it can be prevented to delete easily the important data stored already.
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