| 摘要 |
PURPOSE:To protect data from an erroneous writing by providing an exclusive OR circuit which detects the coincidence between the signal of a medium identifying means and a recording density switching signal and an OR circuit which passes signals of both a write protecting circuit and the exclusive OR circuit. CONSTITUTION:When the signal (e) of recording density from the medium identifying means 12 coincides with the recording density switching signal (a) from a host computer, a write-enable signal is outputted in the form of '0' from the exclusive OR 15. At this time, a NOR circuit 16 outputs '1' when the output of a write protection detecting circuit 11 is '0' (write-enable) or '0' when '1' (write inhibit) since the write-enable signal is '0', thereby indicating write inhibition to the computer. When the signal (e) and signal (a) are not coincident with each other, the write-enable signal becomes '1' and a writing circuit 13 inhibits data from being written regardless of a data signal (c). Then, '0' is generated as the write-enable signal to inhibit the computer 14 from performing writing operation.
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