L6000 datasheet(22/24 Pages) STMICROELECTRONICS

22 / 24 page

for the generation of the Address Mark and

19 cycles 3T patterns of preamble (the pre-

amble’s minimum lenght).

2.WRITE CLOCK should be present and READ

REF CLOCK can be used if the propagation

delay relative to WRT DATA NRZ IN is short.

3.First TWO Address Marks of 7 0s, 1, 7 0s, 1,

11 0s, 1, 11, 0s are output from the WRITE

DATA pin.

4.Next 19 3T patterns (0 1 0 ) are written.

5.At this point, WRT DATA NRZ IN should be

active and inputting the disk data to be writ-

ten. For a longer Preamble, hold WRT DATA

NRZ IN low and more 3T patterns will be gen-

erated.

6.WRITE GATE must be held asserted until all

data is output from the (1, 7) Encoder. There

is a maximum of 15 bits delay, so WRITE

GATE should not deassert until after data has

been flushed from the Encoder.

Hard Sector - Write

The Hard Sector write operation is identical to the

Soft sector, except that at the start, no Address

Mark is generated. WRT DATA NRZ IN should be

held low (rather than have 80 or FF at the start).

The appropriate tables for write precompensation

are:

WRITE PRECOMPENSATION ALGORITHM

RLL Bit Pattern:

Compensation

N-2

N-1

N+1

N+2

BIT N

NONE

EARLY

LATE

LATE: Bit N is time shifted (delayed) from its normal

time position towards the Bit N+1 time position

EARLY: Bit N is time shifted (Advanced) from its nor-

mal time position towards the Bit N-1 time position

Write Precompensation Control

Write precompensation magnitude is set using

the Write Precompensation register. The write

precompensation register bits are defined as fol-

lows:

Bit

Symbol

Description

4-7

WPE

Unused

Write Precomp LSB

Write Precomp

Write Precomp MSB

Write Precomp Enable

W2, W1, W0 - Write precomp magnitude control

bits:

000 > 7x (maximum) shift

001 > 6x shift

010 > 5x shift

011 > 4x shift

100 > 3x shift

101 > 2x shift

110 > 1x shift

111 > No shift

Test Mode

This part has a secondary Write mode. When the

Direct Write bit is set in the Control B register, the

waveform present on the WRT DATA NRZ IN pin

is passed directly through the L6000 to the

preamp WDI pin. This allows for operations like

servowriting to be done with the drive PCB at-

tached to the mechanics. Care should be taken

with the bit in normal system operation.

L6000

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