Sharp FDD-412A - Page 10

FDD412A/B
(4)
Ze
The
The
FDD
reads
out
the
data
from
disk
and
sends
it
to
the
FDC.
The
FDC
searches
the
target
record
as
it
reads
data
on
the
track.
One
record
consists
of
an
ID
part
(identifier)
and
a
data
part.
Reading
the
ID
part
reveals
whether
or
not
the
record
is
what
is
needed.
Index : Index
VY V
IDO ! Data 0 | ID1 ! Data 1 | ID2 : Data 2
{ :
EL RCCOEE Soe
IDn ! Data n
Fig. 2.2 Data Arrangement on Track
The data is read out or written in.
When the target record is found, data is written to or read from
the data part.
The magnetic heads of the FDD are used for both heading and writ-
ing. When a write command is given by the FDC, a current flows in
the magnetic head and all readout operations are suppressed.
That is, the FDD performs either a write or readout operation at
any one time, not both simultaneously. The data read from disk is
of analog waveshapes, which are digitized by the FDD for trans-
mission to the FDC.
The model A FDD incorporates a VFO circuit, and is capable of
demodulating the data that was modulated by the so-called FM/MFM
magnetic recording method.
Configuration
FDD is composed of a drive mechanism and the control electronics,
as shown in Fig. 2.3 (on page 14).
Zerdee
The
reo)
(2)
(3)
1 Drive Mechanism
drive mechanism consists of the following:
Carriage
The carriage is equipped with 2 magnetic heads for side 0 and side
1.
For movement, the carriage receives step motor revolutions via a
steel belt.
Step motor
The step motor turns in response to the STEP-N signal from the
controller.
Step motor revolutions are transmitted via the steel belt to the
carriage which positions the magnetic head at a given location.
Spindle motor
The floppy disk medium is press-fit to the spindle motor by a
collet for rotation.