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1.2 DISK CIRCUITRY
A block diagram of a D2246 disk drive is shown in Figure 1-4. The functional compo-
nents are the interface, the read/write circuits, the servo control, and the motor control
circuits.
~
DISK
DRIVE
CONTROLLE
(SMDI
DC
POWE
- -
R:::::
-
r - -
-
--
LOGIC & SERVO
READ/WRITE
READ DATA/CLOCK
WRITE DATA/CLOCK
J
READPLO&
READ
I
_
SEPARATOR
CIRCUIT
I
-a
"eA,GA"
CONTROL
I
NRZ TO MFM
WRITE
CONVERTER
CIRCUIT
f
j
~SO-9~
I
"eA","m
I
TAG 3
FAUL T SENSE
SMD
I
TAG 2
CONTROL
TAG 1
LSI
!L.
I
HEAD
TAG 4
l
SELECT
-
A
SENSE LINES
SERVO
~
CONTROL
,
l~
LSI
~
I
/I
PHASE
SERVO
UNIT
DETECTOR
PLO
t -
SELECT
It
r-
+
~
t
I
",m,o,
SIGNAL
AGC-AMP
MAPPED
DEMODULATOR
PROFILE
t
VELOCITY
j
GENERATOR
t
__ t5V
r
H
SERVO
~
SERVO
POWER
__ -5V
ANALOG
AMP
f-+-
t12V
AMOTO"
I
r--
-12V
MICRO-PROCESSOR
r--
t24V
CONTROL SYSTEM
(MCSI
/
-, CONTROL
l
AMP
I
POWER AMP
Figure 1-4 D2246 Functional Block Diagram
r
~
DE
ASSEMBLY
"
r
-
H
"eA"WR'"
LSI
I
DATA HEADS
r-
POSITIONER
I
SERVO HEAD
lH
PRE-AMP
r
-
DISK
--,-
SPINDLE
I
MOTOR
L
The interface circuits route data, addresses, status information, and control signals
between the disk drive and the controller.
The read/write circuits control the transfer of data from the disk (read operation), and to
the disk (write operation). During a write operation, the circuits receive serial nonreturn-
to-zero
(NRZ)
format data from the controller and convert the data to a modified
frequency modulation (MFM) format. The MFM data is then written on the disk.
During a read operation, the circuits read and amplify the data from the disk, convert it
from MFM to
NRZ
format, and send the
NRZ
data serially to the controller.
The servo control reads the data prerecorded on the servo disk. The servo control uses
this data to position and maintain the read/write heads on the correct cylinder. The
motor control circuits drive the spindle motor.
1-4
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