Fujitsu MHT2040BH, Product Manual

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4.6 Read/write Circuit
C141-E203-01EN 4-9
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).
Figure 4.4 is a block diagram of the read/write circuit.
4.6.1 Read/write preamplifier (PreAMP)
PreAMP equips a read preamplifier and a write current switch, that sets the bias
current to the MR device and the current in writing. Each channel is connected to
each data head, and PreAMP switches channel by serial I/O. In the event of any
abnormalities, including a head short-circuit or head open circuit, the write unsafe
signal is generated so that abnormal write does not occur.
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 to RLL (Run Length Limited) code data by the encoder circuit then
sent to the PreAMP, and the data is written onto the media.
(1) RLL code MEEPRML
This device converts data using the RLL (Run Length Limited) algorithm.
(2) Write precompensation
Write precompensation compensates, during a write process, for write non-
linearity generated at reading.
Figure 4.4 Read/write circuit block diagram