PC87303 datasheet(36/114 Pages) NSC

36 / 114 page

40 FDC Command Set Description (Continued)

Command Phase

MFM

XXXHDDR1

DR0

Bytes per Sector

Sectors per Track

Format Gap

Data Pattern

Execution Phase

System transfers four ID bytes (track

head sector bytessector) per sector to the floppy control-

ler via DMA or Non-DMA modes The entire track is format-

ted The data block in the Data Field of each sector is filled

with the data pattern byte

Result Phase

Status Register 0

Status Register 1

Status Register 2

Undefined

To allow for flexible formatting the mP must supply the four

Address Field bytes (track head sector bytes per sector

code) for each sector formatted during the Execution

Phase This allows for non-sequential sector interleaving

This transfer of bytes from the mP to the controller can be

done in the DMA or Non-DMA mode with the FIFO enabled

or disabled

The Format Gap byte in the Command Phase is dependent

on the data rate and type of disk drive and controls the

length of GAP3 Some typical values for the programmable

GAP3 are given in Table 4-1

Figure 4-2 shows the track

format for each of the formats recognized by the format

command Table 4-2 shows some typical values for the For-

mat GAP3 based on media type The Format command ter-

minates when the index hole is detected a second time at

which point an interrupt is generated Only the first three

status bytes in the Result Phase are significant

TABLE 4-1 Typical Format GAP3 Length Values Based on Drive Data Rate

Sector

EOT

Sector

Format

Mode

Size

Code

(Hex)

Gap

GAP3

(Decimal)

(Hex)

(Hex) (Note 1)

(Hex) (Note 2)

250 kbps

256

MFM

256

512

1024

2048

4096

500 kbps

256

MFM

512

1024

2048

4096

8192

TABLE 4-2 Typical Format GAP3 Length Values Based on PC Compatible Diskette Media

Media

Sector

EOT

Sector

Format

Type

Size

Code

Hex

Gap

GAP3

Decimal

Hex

360k

512

12M

512

720k

512

144M

512

288M (Note 3)

512

Note 1

Sector Gap refers to the Intersector Gap Length parameter specified in the Command Phase of the Read Write Scan and Verify commands Although

this is the recommended value the FDC treats this byte as a don’t care in the Read Write Scan and Verify commands

Note 2

Format Gap is the suggested value to use in the Format Gap parameter of the Format command This is the programmable GAP3 as shown in

Figure 4-1

Note 3

The 288M diskette media is a Barium Ferrite media intended for use in Perpendicular Recording drives at data rates up to 1 Mbps

PC87303 Datasheet(PDF) 36 Page - National Semiconductor (TI)

PC87303 Datasheet(HTML) 36 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL