PC87413 datasheet(220/257 Pages) NSC

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Revision 1.2

10.0 Legacy Functional Blocks

This chapter briefly describes the following blocks, which provide legacy device functions:

Floppy Disk Controller (FDC).

Parallel Port (PP).

Serial Ports 1 and 2 (SP1 and SP2).

Keyboard and Mouse Controller (KBC).

The description of each Legacy block includes the sections listed below. For details on the general implementation of each

legacy block, see the SuperI/O Legacy Functional Blocks datasheet.

General Description.

Bitmap table(s).

The register maps in this chapter use the following abbreviations for Type:

R/W

= Read/Write.

= Read from a speciﬁc register (write to the same address is to a different register).

= Write (see above).

= Read Only.

= Write Only. Reading from the bit returns 0.

R/W1C = Read/Write 1 to Clear. Writing 1 to a bit clears it to 0. Writing 0 has no effect.

R/W1S = Read/Write 1 to Set. Writing 1 to a bit sets its value to 1. Writing 0 has no effect.

10.1 FLOPPY DISK CONTROLLER (FDC)

10.1.1

General Description

The generic FDC is a standard FDC with a digital data separator and is DP8473 and N82077 software compatible. The PC8741x

FDC supports 14 of the 17 standard FDC signals described in the generic Floppy Disk Controller (FDC) chapter, including:

• FM and MFM modes are supported. To select either mode, set bit 6 of the first command byte when writing to/reading

from a diskette, where:

— 0 = FM mode

— 1 = MFM mode

• A logic 1 is returned during LPC I/O read cycles by all register bits, reflecting the state of floating (TRI-STATE) FDC pins.

Exceptions to standard FDC are:

• Automatic media sense using the MSEN1 signal is not supported.

• DRATE1 is not supported.

Table 59 lists the FDC functional block registers. All registers are VDD powered.

Table 59. FDC Registers

Offset1

Mnemonic

Type

00h

SRA

Status A

01h

SRB

Status B

02h

DOR

Digital Output

R/W

03h

TDR

Tape Drive

R/W

04h

MSR

Main Status

DSR

Data Rate Select

05h

FIFO

Data (FIFO)

R/W

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