PC87351 datasheet(18/86 Pages) NSC

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1.0 Signal/Pin Connection and Description (Continued)

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Signal

Pin/s

I/O

Buffer Type

Description

DENSEL

O4/24

Density Select. Indicates that a high FDC density data rate (500 Kbps or 1

Mbps) or a low density data rate (250 or 300 Kbps) is selected. DENSEL

polarity is controlled by bit 5 of the FDC Conﬁguration Register.

This pin provides an additional density select signal in PPM mode when

PNF = 0.

DIR

OD24-O4/24

Direction. Determines the direction of the Floppy Disk Drive (FDD) head

movement (active = step in, inactive = step out) during a seek operation.

During reads or writes, DIR is inactive.

This pin provides an additional direction signal in PPM mode when

PNF = 0.

DR0

OD24-O4/24

Drive Select 0. Decoded drive select output signal. DR0 is controlled by

Digital Output Register (DOR) bit 0.

DR1

OD24-O4/24

Drive Select 1. Decoded drive select output signal. DR1 is controlled by

Digital Output Register (DOR) bit 1.

This pin provides an additional drive select 1 signal in PPM mode when

PNF = 0.

DRATE0

O6/12

Data Rate 0. Reflects the value of bit 0 of the Conﬁguration Control

written to last. Output from the pin is totem-pole buffered.

This pin provides an additional FDC data rate signal in PPM mode, when

PNF = 0.

DSKCHG

INT

Disk Change. Indicates if the drive door has been opened. The state of this

pin is stored in the Digital Input Register (DIR). This pin can also be

conﬁgured as the RGATE data separator diagnostic input signal via the MODE

command.

This pin provides an additional FDC Disk Change signal in PPM Mode

when PNF = 0.

HDSEL

OD24, O4/24

Head Select. Determines which side of the FDD is accessed. Active low

selects side 1, inactive selects side 0.

This pin provides an additional head select signal in PPM mode when

PNF = 0.

INDEX

INT

Index. Indicates the beginning of an FDD track.

This pin provides an additional index signal in PPM mode when PNF = 0.

MSEN0,

MSEN1

82,

IINT

Media Sense Signals 0 and 1. Provide media sense signals only in PPM

mode when PNF = 0.

MTR0

OD24, O4/24

Motor Select 0. Active low, motor enable line for drive 0, controlled by bits

D7-4 of the Digital Output Register (DOR).

This signal is not available on the PPM, assuming that the external FDD is

either drive 1 or 3.

MTR1

OD24, O4/24

Motor Select 1. Active low, motor enable line for drive 1, controlled by bits

D7-4 of the Digital Output Register (DOR).

This pin provides an additional motor select 1 signal in PPM mode when

PNF = 0. This pin is the motor enable line for drive 1 or drive 0, according

to the TDR Register.

RDATA61

INT

Read Data. Raw serial input data stream read from the FDD.

This pin provides an additional read data signal in PPM mode when PNF = 0.

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