PC97307 datasheet(74/218 Pages) NSC

74 / 218 page

The Digital Floppy Disk Controller (FDC) (Logical Device 3)

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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.

Bits 3,2 - Logical Drive Control (Enhanced TDR

Mode Only)

These read/write bits control logical drive exchange be-

tween drives 0 and 2, only.

They enable software to exchange the physical floppy

disk drive and motor control signals assigned to pins.

Drive 3 is never exchanged for drive 2.

When four drives are configured, i.e., bit 7 of SuperI/O

FDC Configuration register at index F0h is 1, logical

drives are not exchanged.

00 - No logical drive exchange.

01 - Disk drive and motor control signal assignment to

pins exchanged between logical drives 0 and 1.

10 - Disk drive and motor control signal assignment to

pins exchanged between logical drives 0 and 2.

11 - Reserved. Unpredictable results when conﬁgured.

Bits 5,4 - Drive ID1,0 Information

If the value of bits 1,0 of the Digital Output Register

(DOR) are 00, these bits reflect the ID of drive 0, i.e., the

value of bits 1,0, respectively, of the Drive ID register at

index F1h. See “Bits 1,0 - Drive 0 ID” on page 37.

If the value of bits 1,0 of the Digital Output Register

(DOR) are 01, these bits reflect the ID of drive 1, i.e., the

value of bits 3,2, respectively, of the Drive ID register at

index F1h. See “Bits 3,2 - Drive 1 ID” on page 37.

Bit 6 - High Density (Enhanced TDR Mode Only)

Together with bit 7, this bit indicates the type of media

currently in the active floppy disk drive. The value of this

bit reflects the state of the MSEN0 signal.

Table 5-5 shows how these bits encode media type.

TABLE 5-5. Media Type (Density) Encoding

Bit 7 - Extra Density (Enhanced TDR Mode Only)

Together with bit 6, this bit indicates the type of media

currently in the active floppy disk drive. The value of this

bit reflects the state of the MSEN1 signal.

Table 5-5 shows how these bits encode media type.

Bit 7 (MSEN1)

Bit 6 (MSEN0)

Media Type

5.25"

2.88 M

1.44 M

720 K

5.3.5

Main Status Register (MSR), Offset 04h,

Read Operations

This read-only register indicates the current status of the

Floppy Disk Controller (FDC), indicates when the disk con-

troller is ready to send or receive data through the Data

Data Register (FIFO).

The MSR can be read at any time. It should be read before

each byte is transferred to or from the Data Register (FIFO)

except during a DMA transfer. No delay is required when

reading this register after a data transfer.

The microprocessor can read the MSR immediately after a

hardware or software reset, or recovery from a power down.

The MSR contains a value of 00h, until the FDC clock has

stabilized and the internal registers have been initialized.

When the FDC is ready to receive a new command, it re-

ports a value of 80h for the MSR to the microprocessor.

System software can poll the MSR until the MSR is ready.

The MSR must report an 80h value (RQM set to 1) within

2.5 msec after reset or power up.

FIGURE 5-10. MSR Register Bitmap

Bit 0 - Drive 0 Busy

This bit indicates whether or not drive 0 is busy.

It is set to 1 after the last byte of the command phase of

a SEEK or RECALIBRATE command is issued for drive

This bit is cleared to 0 after the first byte in the result

phase of the SENSE INTERRUPT command is read for

drive 0.

0 - Not busy.

1 - Busy.

Bit 1 - Drive 1 Busy

This bit indicates whether or not drive 1 is busy.

It is set to 1 after the last byte of the command phase of

a SEEK or RECALIBRATE command is issued for drive

This bit is cleared to 0 after the first byte in the result

phase of the SENSE INTERRUPT command is read for

drive 1.

0 - Not busy.

1 - Busy.

76543210

Reset

Required

Main Status

Offset 04h

Drive 2 Busy

Non-DMA Execution

Data I/O Direction

RQM

Drive 1 Busy

Drive 3 Busy

Command in Progress

Drive 0 Busy

Read Operations

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