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PC8374T Datasheet(PDF) 12 Page - National Semiconductor (TI) |
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PC8374T Datasheet(HTML) 12 Page - National Semiconductor (TI) |
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12 / 48 page  1.0 Signal/Pin Connection and Description (Continued) www.national.com 12 Revision 1.1 1.4.5 Floppy Disk Controller (FDC) STB_WRITE 51 O OD14, O14/14 VDD3 STB - Data Strobe. When low, Indicates to the printer that valid data is available at the printer port. This signal is in TRI- STATE after a 0 is loaded into the corresponding control register bit. An external 4.7 K Ω pull-up resistor must be connected to this pin. WRITE - Write Strobe. Active low, used in EPP mode to denote an address or data write cycle. When the cycle is aborted, WRITE becomes inactive (high). Signal Pin(s) I/O Buffer Type Power Well Description DENSEL 22 O OD12 O6/12 VDD3 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 17 O OD12 O6/12 VDD3 Direction. Determines the direction of the Floppy Disk Drive (FDD) head movement (active = step in; inactive = step out) during a seek operation. DR0 18 O OD12 O6/12 VDD3 Drive Select. Active low signal controlled by bit 0 of the Digital Output Register (DOR). DRATE0 21 O OD12 O6/12 VDD3 Data Rate. Reflects the value of bit 0 of either Configuration Control Register (CCR) or Data Rate Select Register (DSR), whichever was written to last. DSKCHG 9I INTS VDD3 Disk Change. Indicates that the drive door was opened. HDSEL 10 O OD12 O6/12 VDD3 Head Select. Selects which side of the FDD is accessed. Active (low) selects side 1; inactive selects side 0. INDEX 20 I INTS VDD3 Index. Indicates the beginning of an FDD track. MTR0 19 O OD12 O6/12 VDD3 Motor Select. Active low motor enable signal for drive 0, controlled by bit D4 of the Digital Output Register (DOR). RDATA 11 I INTS VDD3 Read Data. Raw serial input data stream read from the FDD. STEP 16 O OD12 O6/12 VDD3 Step. Issues pulses to the disk drive at a software programmable rate to move the head during a seek operation. TRK0 13 I INTS VDD3 Track 0. Indicates to the controller that the head of the selected floppy disk drive is at track 0. WDATA 15 O OD12 O6/12 VDD3 Write Data. Carries out the pre-compensated serial data that is written to the FDD. Pre-compensation is software selectable. WGATE 14 O OD12 O6/12 VDD3 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 12 I INTS VDD3 Write Protected. Indicates that the disk in the selected drive is write protected. Signal Pin(s) I/O Buffer Type Power Well Description |
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