CIRCUIT FOR DETECTING UNRECORDED PORTION OF RECORDING MEDIUM

CIRCUIT POUR DETECTER LES PARTIES NON ENREGISTREES D'UN SUPPORT D'ENREGISTREMENT

English Abstract

Disclosed is a circuit for detecting an unrecorded portion in a recording
medium,
which comprises a window counting portion (10) for receiving an input signal
to
recognize if the input signal comes from an unrecorded portion of the
recording medium
and counting a predetermined time to generate a window pulse signal, and a
sync signal
generator (20) which is enabled by the window pulse signal, in which if the
number of
pulses of the input signal is not less than a predetermined number, the
generator
recognizes the current input signal comes from a data region of the recording
medium to
simultaneously generate a sync signal, while if the number of pulses of the
input signal
is not more than a predetermined number of pulses, the generator recognizes
the current
input signal comes from an unrecorded region of the recording medium, not to
generate
the sync signal. The unrecorded portion is accurately detected not to generate
a sync
signal due to noise included in the unrecorded portion of the recording
medium.

French Abstract

Circuit permettant de détecter une partie non enregistrée d'un support d'enregistrement, qui comprend une section (10) de comptage de fenêtres destinée à recevoir un signal d'entrée pour reconnaître si le signal d'entrée vient d'une partie non enregistrée du spport d'enregistrement et à compter un laps de temps prédéterminé pour générer un signal d'impulsion de fenêtre, et un générateur (20) de signaux de synchronisation qui est mis en service par le signal d'impulsion de fenêtre. Si le nombre d'impulsions du signal d'entrée n'est pas inférieur à un nombre prédéterminé le générateur reconnaît que le signal d'entrée concerné vient d'une région de données du support d'enregistrement et génère simultanément un signal de synchronisation. Mais si le nombre d'impulsions du signal d'entrée n'est pas supérieur à un nombre prédéterminé d'impulsions, le générateur reconnaît que le signal d'entrée concerné vient d'une région non enregistrée du support d'enregistrement et ne génère pas de signal de synchronisation. La partie non enregistrée est détectée avec précision, de manière à ce qu'un signal de synchronisation ne soit pas généré sur la base du bruit présent sur la partie non enregistrée du support d'enregistrement.

Claims

7
CLAIMS:
1. A circuit for detecting an unrecorded portion in a recording medium,
comprising:
window counting means for receiving a signal to recognize that the signal
comes
from an unrecorded portion of the recording medium and for generating a window
pulse
signal by counting a predetermined time; and
sync signal generating means which is enabled by said window pulse signal, in
which if the number of pulses of the input signal is not less than a
predetermined number,
said sync signal generating means recognizes the current input signal comes
from a data
region of the recording medium to simultaneously generate a sync signal, while
if the
number of pulses of the input signal is not more than a predetermined number,
said sync
signal generating means recognizes the current input signal comes from an
unrecorded
region of the recording medium, not to thereby generate the sync signal.
2. The circuit for detecting an unrecorded portion in a recording medium
according to claim 1, wherein said window counting means comprises unrecorded
portion
recognition means for receiving said input signal and recognizing that said
input signal
comes from the unrecorded portion of the recording medium, storage means for
storing
the output of said unrecorded portion recognition means and generating the
output of said
unrecorded portion recognition means in response to said input signal, window
forming
means which is enabled by the output of said storage means and for counting a
predetermined time in response to a predetermined clock to form a window
signal.
3. The circuit for detecting an unrecorded portion in a recording medium
according to claim 2, wherein said sync signal generating means comprises a
pulse
counter/sync generator which is enabled in response to the output of said
window forming
means and for receiving said input signal to then generate a certain pulse
signal if a

8
predetermined number of pulses are input, and on the other hand not to then
generate said
certain pulse signal if the predetermined number of pulses are not input, and
means for
logical summing of the outputs of both said unrecorded portion recognition
means and
the pulse counter/sync generator to output the sync signal.
4. The circuit for detecting an unrecorded portion in a recording medium
according to claim 1, wherein said unrecorded portion detection circuit
further comprises
sync signal corrector means for receiving the output of said sync signal
generating means
and for generating an accurate sync signal.
5. The circuit for detecting an unrecorded portion in a recording medium
according to claim 2, wherein said window forming means detects the rising
edge of the
first noise pulses included in said unrecorded portion to then generate the
rising edge of
a window signal, and counts a predetermined time to then generate the falling
edge of the
window signal.

Description

2120510
CIRCUIT FOR DETECTING UNRECORDED
PORTION OF RECORDING MEDIUM
TECHNICAL FIELD
The present invention relates to a magnetic storage device, and more
particularly,
to a circuit for detecting an unrecorded portion in a magnetic recording
medium.
BACKGROUND ART
In general, a magnetic recording medium includes a sector identification code
for
distinguishing one sector from another. Also, there is an unrecorded portion
between
respective sectors. It should be noted that, since noise is generated in
unrecorded portions
of such a magnetic recording medium, a sync signal may not be generated at the
exact
starting point of a sector. That is, since the noise generated in an
unrecorded portion may
be mistaken for the starting point of a sector, the sync signal may be
generated in the
unrecorded portion.
FIG.IA represents the conventional data recording format of a hard disk.
In FIG. IA, a post-amble portion exists from an end location ENDS to a
starting
point of an unrecorded portion DC-GAP, sequentially followed by an unrecorded
portion,
a pre-amble portion and a data portion.
FIG. l B shows the location where a normal sync signal is generated in a
conventional hard disk. Here, it can be seen that the normal sync signal is
generated at
a predetermined point of the pre-amble portion.
FIG.2 shows the location where a sync signal is generated in a conventional
hard
disk when one or two noise pulses included in the unrecorded portion are
mistaken for

2
a data signal. Thus, the conventional unrecorded portion detecting circuit of
the recording
medium erroneously generates a sync signal by recognizing as data pulses the
noise
pulses in the unrecorded portion of the recording medium.
DISCLOSURE OF THE INVENTION
Therefore, to solve the above problems, it is an object of the present
invention to
provide a circuit for detecting unrecorded portion in which, when unrecorded
portion is
detected, a starting point of a sector is accurately detected by ignoring
noise pulses,
thereby generating a desired sync signal.
To accomplish the above object of the present invention, there is provided a
circuit for detecting unrecorded portion in a recording medium, comprising:
window counting means for receiving a signal to recognize that the signal
comes
from an unrecorded portion of the recording medium and for generating a window
pulse
signal by counting a predetermined time; and
sync signal generating means which is enabled by the window pulse signal, in
which if the number of pulses of the input signal is not less than a
predetermined number,
said sync signal generating means recognizes the current input signal comes
from a data
region of the recording medium to simultaneously generate a sync signal, while
if the
number of pulses of the input signal is not more than a predetermined number,
said sync
signal generating means recognizes the current input signal comes from an
unrecorded
region of the recording medium, not to thereby generate the sync signal.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will become apparent
from
the following description of the invention which refers to the accompanying
drawings:

3 ~12~~
FIG.1 A represents a conventional data recording format for a hard disk;
FIG.1B shows the location where a desired sync signal is generated in a
conventional hard disk;
FIG.2 shows the location where a sync signal is generated in a conventional
hard
S disk when one or two noise pulses included in the unrecorded portion are
mistaken for
a data signal;
FIG.3 is a block diagram of one embodiment of an unrecorded portion detecting
circuit according to the present invention; and
FIG.4 is a timing diagram for explaining an operation of an unrecorded portion
detecting circuit shown in FIG.3.
BEST MODE FOR CARRYING OUT THE INVENTION
The preferred embodiment of an unrecorded portion detecting circuit according
to the present invention will be described below in more detail with reference
to the
accompanying drawings.
In FIG.3, an unrecorded portion detecting circuit according to the present
invention comprises a window counting portion 10 for receiving read/write
pulse signal
and recognizing that the read/write signal comes from an unrecorded portion of
a
recording medium and generating a window signal by counting a predetermined
time in
response to a clock signal, and a sync signal generator 20 which is enabled by
window
counting means 10 for accurately generating a sync signal by determining if
the number
of pulses of the read/write signal is not less than a predetermined number of
pulses.
Window counting portion 10 comprises unrecorded portion recognition device 100
for receiving the read/write signal and determining if the signal comes from
the data
region or the unrecorded region of the recording medium, a D-type flip-flop
200 which

2~~~.
4
has a data input terminal D for receiving the output of the unrecorded portion
recognition
device 100 and a clock terminal for receiving the read/write signal, and
window forming
device 300 which has a clear terminal CLR for receiving the output of D-type
flip-flop
200 and a system clock terminal, wherein said window forming device 300 is
enabled by
the system clock and counts a predetermined time so as to form a window by
performing
a transition of a pulse state.
Sync signal generator 20 comprises a pulse counter/sync generator 400 having a
clock terminal for receiving the read/write signal and a clear terminal
cleared by the
output of window forming device 300, thereby counting the number of pulses of
the input
signal to accordingly generate a sync signal, and an OR gate 500 for receiving
the outputs
of both unrecorded portion recognition device 100 and pulse counter/sync
generator 400
to logically sum both the signals and to accordingly generate a sync signal.
FIG.4 is a timing diagram for explaining an operation of a preferred
embodiment
of the unrecorded portion detecting circuit shown in FIG.3.
In FIGs.3 and 4, if the number of input continuous pulses is less than or
equal to
two, it is assumed that the input pulses are noise. Unrecorded portion
recognition means
100 receives data which has been read out from the magnetic recording medium
and
recognizes that the input signal comes from the unrecorded portion of the
magnetic
recording medium. D-type flip-flop 200 receives the output of unrecorded
portion
recognition device 100 and then if the input signal is received through the
clock terminal,
a pulse is generated. Window forming nleans 300 counts a predetermined time in
responsive to the system clock and generates the window pulse signal, if the
output of D-
type flip-flop 200 is input to the clear terminal CLR. Here, the above
predetermined time
is a time during which three pulse signals can be input. As shown in Fig.4,
window
forming means 300 detects the rising edge of a first noise pulse of the input
signal

...
212010
s
included in the unrecorded portion to generate a rising edge of a window
signal, and then
counts a predetermined time to generate a falling edge of the window signal.
Pulse
counter/sync generator 400 generates a sync signal if the number of pulses of
the signal
input during an enabled period of the output of window forming device 300 is
more than
or equal to three, while pulse counter/sync generator 400 recognizes the input
signal as
noise so as not to generate the sync signal if the number of pulses of the
signal input
during the same period is less than or equal to two. That is, pulse
counter/sync generator
400 detects a rising edge of the third pulse and generates a sync signal when
it is
determined that three pulses are input. Accordingly, logical summing device
s00 outputs
the sync signal only when the output of pulse counter/sync generator 400 is
generated.
The generated sync signal is generated as being slightly delayed from the
desired
sync signal. Thus, it is necessary to add a sync signal correction circuit for
synchronizing
the desired sync signal with the sync signal appearing at the output side of
logical
summing device s00 shown in FIG.3. By doing so, correction of the sync signal
is
is simply performed.
The above-described embodiment has been explained under the assumption that
if one or two pulses are input, the input pulses are noise. However, in other
embodiments, both the window counting device and the sync signal generator may
form
a window signal with respect to the input signal more than or equal to a
predetermined
number of pulses, count the number of the input pulses and determine whether
or not the
input pulses are noise.
The above-described unrecorded portion detecting circuit according to the
present
invention counts the predetermined time to form the window pulse in window
forming
device 300, and generates the sync signal if not less Chall the predetermined
number of
pulses is input within the counted interval in pulse counter/sync generator
400 while if

~~~o~lo
6
the predetermined number of pulses is not input, it is determined as noise so
as not to
finally generate the sync signal.
As descr~bed above, the unrecorded portion detecting circuit according to the
present invention accurately detects the unrecorded portion not to generate a
sync signal
due to noise included in the unrecorded portion of the recording medium.
Accordingly,
the present invention can improve reliability of electronic products requiring
accurate
synchronization.
INDUSTRIAL APPLICATION
The present invention can be widely applied in the field of the electronic
household products in which signals are recorded and reproduced using
recording media.

Representative Drawing