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PC87393F Datasheet(PDF) 19 Page - National Semiconductor (TI) |
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PC87393F Datasheet(HTML) 19 Page - National Semiconductor (TI) |
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19 / 148 page  1.0 Signal/Pin Connection and Description (Continued) 19 www.national.com 1.5.4 Floppy Disk Controller (FDC) Signal Pin(s) I/O Buffer Type Power Well Description DENSEL 33, 53 O O2/12 VDD Density Select. Indicates that a high FDC density data rate (500 Kbps, 1 Mbps or 2 Mbps) or a low density data rate (250 or 300 Kbps) is selected. DIR 29, 49 O OD12,O2/12 VDD Direction. Determines the direction of the Floppy Disk Drive (FDD) head movement (active = step in, inactive = step out) during a seek operation. DR1 DR0 41, 71, 72 30 OOD12,O2/12 VDD Drive Select. Decoded output signals in 2-drive mode, or encoded signals in 4-drive mode. Controlled by bits 1 and 0 of the Digital Output register (DOR). DRATE0 34, 73 O O3/6 VDD Data Rate 0. Reflects the value of bit 0 of the Configuration Control register (CCR) or the Data Rate Select register (DSR), whichever was written to last. DRATE1 53 O O3/6 VDD Data Rate 1. Reflects the value of bit 1 of the Configuration Control register (CCR) or the Data Rate Select register (DSR), whichever was written to last. Available on the PPM pins only. DSKCHG 21, 45 I INT VDD Disk Change. Indicates if the drive door has been opened. HDSEL 22, 51 O OD12,O2/12 VDD Head Select. Determines which side of the FDD is accessed. Active low selects side 1, inactive selects side 0. INDEX 32, 52 I INT VDD Index. Indicates the beginning of an FDD track. MSEN1, 0 42, 44 I INT VDD Automatic Media Sense. Identifies the media type of the floppy disk in drive 1 and 0, if the drive supports this protocol. MTR1 MTR0 84, 73, 40 31 OOD12,O2/12 VDD Motor Select. Active low, motor enable lines for drive 1 and 0, controlled by bits D7-4 of the Digital Output register (DOR). MTR0 is used to decode DR1 and DR0 in 4-drive mode. RDATA 23, 46 I INT VDD Read Data. Raw serial input data stream read from the FDD. STEP 28, 47 O OD12,O2/12 VDD Step. Issues pulses to the FDD at a software programmable rate to move the head during a seek operation. TRK0 25, 50 I INT VDD Track 0. Indicates to the controller that the head of the selected FDD is at track 0. WDATA 27, 37 O OD12,O2/12 VDD Write Data. Carries out the pre-compensated serial data that is written to the FDD. Pre-compensation is software selectable. WGATE 26, 36 O OD12,O2/12 VDD Write Gate. Enables the write circuitry of the selected FDD. WGATE is designed to prevent glitches during power-up and power-down. This prevents writing to the disk when power is cycled. WP 24, 48 I INT VDD Write Protected. Indicates that the disk in the selected drive is write protected. |
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