| 摘要 |
PURPOSE:To use an optional floppy disc drive (FDD) by providing a circuit which switches the selection object FDD of an FDD selecting signal. CONSTITUTION:When a switch 12 is turned off, AND gates 5 and 7 are opened, and AND gates 4 and 6 are closed, and an FDD select signal SELECT1 outputted from a floppy disc controller FDC 3 is inputted to an external FDD 2 through the AND gate 7 and an OR gate 11 to select this FDD. An FDD select signal SELECT2 outputted from the FDC 3 is inputted to an FDD 1 through the AND gate 5 and an OR gate 10 to select this FDD. Though only the external FDD 2 can be used, the switch 12 is turned off to give flexibility to the FDD select signal outputted from the FDC 3, and an optional FDD can be used.
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