PC97338 datasheet(79/221 Pages) NSC

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3.3.5

Tape Drive Register (TDR),

Offset 011

The TDR register is a read/write register that acts as

the Floppy Disk Controller’s (FDC) media and drive

type register.

The bits of the TDR register function differently, de-

pending on the drive mode configured by bit 0 of the

Function Control configuration Register (FCR) (page

48), bit 2 of the Advanced SuperI/O Chip (ASC) con-

figuration register (page 52) and bits 1 and 0 of Su-

perI/O Chip configuration register 2 (SCF2) (page 58).

See Table 38.

The TDR drive modes are:

• PC-AT Compatible

• Automatic Media Sense

• Enhanced

PC-AT Compatible TDR Drive Mode

When bit 0 of FCR is 1, and bit 2 of ASC is 0, the TDR

assigns a drive number to the tape drive support

mode of the data separator. All other logical drives

can be assigned as floppy drive support. Bits 7-2 are

in TRI-STATE during read operations.

Automatic Media Sense TDR Drive Mode

When bit 0 of FCR is 0, and bit 2 of ASC is 0, bits 7-5

of TDR are implemented, in addition to the bits that

support Compatible AT TDR mode. Bits 4-2 are re-

served.

Enhanced TDR Drive Mode

When bit 0 of FCR is 0, and bit 2 of ASC is 0, the TDR

uses all its bits for operation with PS/2 floppy disk

drives, except for bit 4 which is reserved.

FIGURE 48. TDR Register Bitmap

Bits 1,0 - Tape Drive Select 1,0

These bits assign a logical drive number to a tape

drive. Drive 0 is not available as a tape drive and

is reserved as the floppy disk boot drive.

00 - No drive selected.

01 - Drive 1 selected.

10 - Drive 2 selected.

11 - Drive 3 selected.

654

Reset

Required

Tape Drive

Offset 011

Reserved

Valid Data

High Density

Extra Density

Tape Drive Select1,0

Logical Drive Control 1,0

Automatic Media Sense

and Enhanced TDR Drive

Enhanced TDR Drive Mode Only

Modes Only

TABLE 38. TDR Bit Utilization and Reset Values in Different Drive Modes

TDR Drive Mode

Bit 0

FCR

Bit 2

ASC

Bits of TDR

Extra

Density

High

Density

Valid

Data

Reserved

Logical Drive

Control

Drive Select

765

PC-AT Compatible

Not used. In TRI-STATE during read operations.

Automatic Media

Sense

Not

Reset

Not

Reset

Not

Reset

Reserved

Enhanced

0 or 1

Not

Reset

Not

Reset

Not

Reset

000

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