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FUJITSU MHA2032AT User Manual

Page 50

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Theory of Device Operation

4-10

C141-E042-01EN

signal (WUS) when a write error occurs due to head short-circuit or head
disconnection.

4.6.2 Write circuit

The write data is output from the hard disk controller (HDC) with the NRZ data
format, and sent to the encoder circuit in the RDC with synchronizing with the
write clock. The NRZ write data is converted from 8-bit data to 9-bit data by the
encoder circuit then sent to the PreAMP, and the data is written onto the media.

(1) 8/9 GCR

The disk drive converts data using the 8/9 (0, 4, 4) group coded recording (GCR)
algorithm. This code format is 0 to 4 code bit “0”s are placed between “1”s.

(2) Write precompensation

Write precompensation compensates, during a write process, for write non-
leneartiry generated at reading. Table 4.2 shows the write precompensation
algorithm.

Table 4.2 Write precompensation algorithm

Bit

Bit

Bit

Compensation

n – 1

n

n + 1

Bit n

0

1

1

None

1

1

0

Late

1

1

1

Late

Late: Bit n is time shifted (delayed) from its nominal time position towards the

bit n+1 time position.

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