Filter
Top Products
C141-E077-01EN 4 - 11
4.6 Read/write Circuit
The read/write circuit consists of the read/write preamplifier (PreAMP), the write circuit, the
read circuit, and the time base generator in the read channel (RDC).
4.6.1 Read/write preamplifier (PreAMP)
One PreAMP is mounted on the FPC. The PreAMP consists of an 4 or 8-channel read
preamplifier and a write current switch and senses a write error. Each channel is connected to
each data head. The head IC switches the heads by the serial port (SDEN, SCLK, SDATA).
The IC generates a write error sense 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 16-bits data to 17-bits 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, 6, 8) group coded recording (GCR) algorithm.
This code format is 0 to 6 code bit "0"s are placed between "1"s.
(2) Write precompensation
Write precompensation compensates, during a write process, for write non-linearity generated
at reading.
4.6.3 Read circuit
The head read signal from the PreAMP is regulated by the automatic gain control (AGC)
circuit. Then the output is converted into the sampled read data pulse by the programmable
filter circuit and the adaptive equalizer circuit. This clock signal is converted into the NRZ
data by the 16/17 GCR decoder circuit based on the read data maximum-likelihood-detected
by the Viterbi detection circuit, then is sent to the HDC.
(1) AGC circuit
The AGC circuit automatically regulates the output amplitude to a constant value even when
the input amplitude level fluctuates. The AGC amplifier output is maintained at a constant
level even when the head output fluctuates due to the head characteristics or outer/inner head
positions.