PC87309VLJ datasheet(56/192 Pages) NSC

56 / 192 page

The Floppy Disk Controller (FDC) (Logical Device 0)

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Result Phase

After a hardware or software reset, parameters in this phase

are reset to their default values. Some of these parameters

are unaffected by a software reset, depending on the state

of the LOCK bit.

See the command that determines the setting for the bit or

field for details.

First through Fourth Result Phase Bytes, Bits 7-0,

Present Track Number (PTR) Drives 3-0

Each of these bytes contains either the internal 8-bit

track number or the least signiﬁcant byte of the 12-bit

track number of the corresponding logical disk drive.

Fifth and Sixth Result Phase Bytes, Bits 7-0,

Step Rate Time, Motor Off Time, Motor On Time and DMA

These fields are all set by the SPECIFY command. See

Section 3.7.21 on page 73.

Seventh Result Phase Byte -

Sectors Per Track or End of Track (EOT)

This byte varies depending on what commands have

been previously executed.

If the last command issued was a FORMAT TRACK

command, and no read or write commands have been

issued since then, this byte contains the sectors per

track value.

If a read or a write command was executed more recent-

ly than a FORMAT TRACK command, this byte speci-

fies the number of the sector at the End of the Track

(EOT).

Eighth Result Phase Byte

Bits 5-0 - DC3-0, GDC

Bits 5-0 of the second command phase byte of the PER-

PENDICULAR MODE command set bits 5-0 of this byte.

See “Bits 5-2 -Drive 3-0 Mode Configuration (DC3-0)”

on page 63.

Bit 7 - LOCK

This bit controls how the other bits in this command re-

spond to a software reset. See Section 3.7.6 on page

60.

The value of this is determined by bit 7 of the opcode of

the LOCK command.

0: Bits in this command are set to their default values

after a software reset. (Default)

1: Bits in this command are unaffected by a software

reset.

Ninth and Tenth Result Phase Bytes

These bytes reflect the values in the third and fourth

command phase bytes of the CONFIGURE command.

See Section 3.7.2 on page 55.

3.7.4

The FORMAT TRACK Command

This command formats one track on the disk in IBM, ISO, or

Toshiba perpendicular format.

After a pulse from the INDEX signal is detected, data pat-

terns are written on the disk including all gaps, Address

Marks (AMs), address fields and data fields. See FIGURE

3-5 on page 59.

The format of the track is determined by the following pa-

rameters:

The MFM bit in the opcode (first command) byte, which

indicates the type of the disk drive and the data transfer

rate and determines the format of the address marks

and the encoding scheme.

The Index Address Format (IAF) bit (bit 6 in the second

command phase byte) in the MODE command, which

selects IBM or ISO format.

The Group Drive Configuration (GDC) bits in the PER-

PENDICULAR MODE command, which select either

conventional or Toshiba perpendicular format.

A bytes-per-sector code, which determines the sector

size. See TABLE 3-10 on page 57.

A sectors per track parameter, which specifies how

many sectors are formatted on the track.

The data pattern byte, which is used to fill the data field

of each sector.

TABLE 3-9 on page 57 shows typical values for these pa-

rameters for specific PC compatible diskettes.

To allow flexible formatting, the microprocessor must sup-

ply the four address field bytes (track number, head num-

ber, sector number, bytes-per-sector code) for each sector

formatted during the execution phase. This allows non-se-

quential sector interleaving.

This transfer of bytes from the microprocessor to the con-

troller can be done in DMA or non-DMA mode (See Section

3.4.2 on page 45), with the FIFO enabled or disabled.

The FORMAT TRACK command terminates when a pulse

from the INDEX signal is detected a second time, at which

point an interrupt is generated.

76543210

Byte of Present Track Number (PTR) Drive 0

Byte of Present Track Number (PTR) Drive 1

Byte of Present Track Number (PTR) Drive 2

Byte of Present Track Number (PTR) Drive 3

Step Rate Time (SRT)

Delay After Processing

Delay Before Processing

DMA

Sectors per Track or End of Track (EOT) Sector #

LOCK

DC3

DC2

DC1

DC0

GDC

EIS

FIFO POLL

THRESH

Precompensation Track Number (PRETRK)

PC87309VLJ データシート(PDF) 56 Page - National Semiconductor (TI)

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