Write Circuit - Fujitsu MHG2102AT - Mobile 10 GB Hard Drive Product Manual

Theory of Device Operation
signal (WUS) when a write error occurs due to head short-circuit or head
disconnection.
The Pre AMP sets the write current and bias current which flows through MR
devices.

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. The NRZ write data is
converted from 16-bit data to 17-bit data by the encoder circuit then sent to the
PreAMP, and the data is written onto the media.
(1) 16/17 GCR
The disk drive converts data using the 16/17 (0, 12, 8) group coded recording
(GCR) algorithm. This code follows a format in which 0 to 12 "0"s are inserted
while the code bit is "1" and 0 to 8 "0"s are inserted while the 0DD/EVEN bit is
"1".
(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
4-10
Bits Compensation
111001
111010
:
111111
000000
000001
:
010000
:
100000
–7
–6
–1
0
+1
+16
+32
C141-E070-01EN