DP8496 datasheet(30/92 Pages) NSC

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40 Functional Description (Continued)

TABLE 414 Register Addresses for Format of ID Segment (Hex)

PSIG

Hdr

Snyc1

Snyc2

Hdr0

Hdr1

Hdr2

Hdr3

Hdr4

Hdr5

CRC

Hdr

Gap

Prmbl

ECC

Post

Pattern

auto

Control

Range

1 – FF

1 – 7

0 – 1F

0 – 7

0 – 1F

0 – 1

0 – 7

3 – 1F

TABLE 415 Register Addresses for Format of Data Segment (Hex)

Data

Sync1

Sync2

Data Field

CRC

Data

Gap3

Gap

Prmbl

ECC

Post

Pattern

auto

Control

35 36

Range

1 – 7

0 – 1F

0 – 7

0 – 1F

10 – FFFE (Must Be Even)

0 – 7

1 – 1F

1 – FF

Header Preamble

Sets the number of bytes in the Header Preamble for the

PLL to lock to The pattern used is from the Preamble Pat-

tern register Range is 0 – 1F

Preamble Pattern (PREP)

22h

76543210

Pattern

Pattern used for the Header Gap Header Preamble Data

Gap and Data Preamble fields This pattern must be all

zeros for a soft-sectored drive

Header Sync

2 Count (HSC) 23h

76543210

Synch

Sets the number of bytes in the Synch

1 and Synch

fields The range of Synch

1 is 0 – 7 The range of Synch

2is0 – 1F

Both Synch

1 and Synch

2 cannot be zero

At least one must be non-zero

For soft sectored drives AME is generated while writing the

Synch

1 field to the disk AMF is expected while reading

Synch

1 from the disk

Header Synch

1 Pattern (HSP1) 24h

76543210

Pattern

Pattern used for the Synch

1 field Can be used as an

Address Mark in soft sectored formats

Header Synch

2 Pattern (HSP2) 25h

76543210

Pattern

Pattern used for the Synch

2 field

Header Byte 01 Control (HC01)

26h

76543210

NC0

SM0

SN0

HB0

NC1

SM1

SN1

HB1

This register does not perform any pattern repetition nor

does it define a field size It is provided to control the func-

tion of each corresponding header byte There is one Head-

er Byte Control register for each pair of the six Header Byte

Pattern registers The upper four bits correspond to one pat-

tern register The lower four bits correspond to another pat-

tern register

NC Not Compared

This header byte will always match true for a Compare

Header operation

This header byte will be compared normally without

modification of the outcome

SM Header Failed Although Sector Matched Enable

The Header Failed Although Sector Matched function is

enabled for this header byte While searching for a

matching Header Segment if this field matches while

other header bytes don’t an error is reported in the

Disk Status register Typically this would be the sector

number field See Section 434 for additional informa-

tion

The Header Failed Although Sector Matched function is

not enabled for this header byte

SN Sector Number Substitution

The contents of the Sector Number register are substi-

tuted for this Header Byte pattern during a Write Head-

er operation and compared during a Compare Header

operation This is normally used in multi-sector com-

mands

The contents of the Header Byte Pattern register is writ-

ten to the disk for a Write Header operation and com-

pared during a Compare Header operation

DP8496 Datasheet(PDF) 30 Page - National Semiconductor (TI)

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