PC87391 datasheet(42/148 Pages) NSC

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2.0 Device Architecture and Configuration (Continued)

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2.10.6

SuperI/O Configuration 5 Register (SIOCF5)

Location:

Index 25h

Type:

Varies per bit

Bit

76543210

Name

PNF Status

Pin 35

Function

Select

SMI to IRQ2

Enable

Pin 34

Function

Select

PPM Power

Save Enable

Pin 71

Function

Select

Reset

10000000

Bit

Description

PNF Status. This bit describes the status of the PNF signal, which determines if Parallel Port of external FDD sig-

nals are selected by PPM mode. This is a RO bit.

0: Floppy Disk

1: Parallel Port (default)

6-5

Pin 35 Function Select. These are R/W bits.

Bits

Function

6 5

0 0

PPM disabled (default)

0 1

PNF signal selected as active low (high selects printer, low selects floppy)

1 0

PNF signal selected as active high (low selects printer, high selects floppy)

1 1

XRDY signal selected

SMI to IRQ2 Enable. This is a R/W bit.

0: Disabled (default)

1: Enabled

Pin 34 Function Select. This is a R/W bit.

0: DRATE0 (default)

1: IRSL2

PPM Power Save Enable

0: Disabled (default).

1: When PPM is active and PNF is 0 (bit 7 of this register), the FDC output pins and the Parallel Port output

pins are masked when the corresponding drive is not used.

1-0

Pin 71 Function Select.1 This is a R/W bit.

Bits

Function

1 0

0 0

GPIO37 (default)

0 1

DR1

1 0

IRSL2

1 1

XIORD

In the PC87391, this pin is pulled up after reset by an internal pull-up resistor. Software should set this ﬁeld as

appropriate to enable the required Legacy function.

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