Method for reading a synchronizing signal from a record medium and an apparatus therefor

Claim 2

A synchronizing signal reading apparatus for a recording medium comprising: an address portion and a data portion with synchronizing pattern data at the head thereof, said data portion being divided into a plurality of portions to form re-synchronizing pattern data between the divided data portions to provide a sector, a synchronizing pattern detecting means for detecting said synchronizing pattern data provided at the head of said data portion read from said recording medium on which a plurality of sectors are formed on a track; re-synchronizing pattern detecting means for detecting re-synchronizing pattern data provided between the divided data portion read from said recording medium; synchronizing pattern detecting judging means for judging whether the detection by said synchronizing pattern detecting means is successful; re-synchronizing pattern detecting judging means for judging within a predetermined period whether the detection by said re-synchronizing pattern detecting means is successful; and control means for, when said synchronizing pattern detecting judging means judges that a detection of said synchronizing pattern has failed, extending a time period for detecting by said re-synchronizing pattern detecting judging means based on the judgment by said synchronizing pattern detecting judging means.

Claim 3

The synchronizing signal reading apparatus according to claim 2, wherein said re-synchronizing pattern detecting means and said re-synchronizing pattern detection judging means comprises: re-synchronizing pattern data storing means for storing said re-synchronizing pattern data; a first reading data storing means for storing the piece of serial data having the same bit number as the latest piece of re-synchronizing pattern data read from said recording medium; a first comparing means for judging whether the first piece of read out data stored in said first reading data storing means is equal to the piece of re-synchronizing pattern data stored in said re-synchronizing pattern data storing means; a first effective time period setting means for setting a first effective time period in which said first comparing means performs a comparison of said two pieces of data; a second effective time period setting means for setting a second effective time period in which said first comparing means performs a comparison in a time period which is longer in the backward and/or forward directions than the first effective time period set by said first effective time period setting means; and said control means controls said synchronizing pattern detecting judging means so that, when it succeeds in detecting said synchronized pattern data, said first comparing means performs a comparison during the first effective time period set by said first effective time period setting means such that, when it fails to detect said synchronizing pattern data, said first comparing means performs the comparison during the effective time period determined by said second effective time period setting means.

Claim 4

The synchronizing signal reading apparatus according to claim 3, wherein said first effective time period setting means comprises: a first counter for performing a count operation in synchronization with a clock of a first frequency; a first count value storing means for storing a first count value; a second count value storing means for storing a second value; a second comparing means for detecting whether the count value of said first counter accords with the first count value stored in said first count value storing means and for enabling said first comparing means to start a comparison operation when both count values are consistent; and a third comparing means for detecting whether said count value of the first counter accords with the second count value stored in the second count value storing means, for enabling said first comparison means to start the comparison operation, and ensuring that the count value of the first counter accords with the second count value.

Claim 5

The synchronizing signal reading apparatus according to claim 3, wherein said second effective time setting means comprises a second counter for performing a count operation in synchronization with the second clock of the second frequency; a third count value storing means for storing the third count value; a fourth count value storing means for storing the fourth count value; a fourth comparison means for detecting whether the count value of the third counter accords with the third count value stored in the third count value storing means and for enabling said first comparison means to start the comparison operation when both count values accord with each other and the a fifth comparison means for detecting whether the count value of the second counter accords with the fourth count value stored in the fourth count value storing means and for enabling said first comparison means to stop the comparison operation when both count values accord with each other.

Claim 6

The synchronizing signal reading apparatus according to claim 4, wherein said second effective time setting means comprises a second counter for performing a count operation in synchronization with the second clock of the second frequency; a third count value storing means for storing the third count value; a fourth count value storing means for storing the fourth count value; a fourth comparison means for detecting whether the count value of the third counter accords with the third count value stored in the third count value storing means and for enabling said first comparison means to start the comparison operation when both count values accord with each other; and a fifth comparison means for detecting whether the count value of the second counter accords with the fourth count value stored in the fourth count value storing means and for enabling said first comparison means to stop the comparison operation when both count values accord with each other.

Claim 7

The synchronizing signal reading apparatus according to claim 3, wherein said second effective time period setting means comprises a third counter for performing a counting operation in synchronization with the clock of the third frequency; a fifth count value storing means for storing a fifth count value; a sixth count value storing means for storing a sixth count value; a selection means for selecting said fifth count value stored in said fifth count value storing means or the sixth count value stored in said sixth count value storing means; and a fifth comparing means for comparing said fifth count value selected by said selecting means with the count value of said third counter, enabling said first comparing means to start a comparison operation when the count value of the third counter accords with the fifth count value, enabling said selection means to select the sixth count value, comparing the sixth count value output from said selection means with a count value of the third counter and enabling said first comparing means to stop a comparison operation when said count value of the third counter accords with the sixth count value.

Claim 8

The synchronizing signal reading apparatus according to claim 4, wherein said second effective time setting means comprises a second counter for performing a count operation in synchronization with the second clock of the second frequency; a third count value storing means for storing the third count value; a fourth count value storing means for storing the fourth count value; a fourth comparison means for detecting whether the count value of the third counter accords with the third count value stored in the third count value storing means, and for enabling said first comparison means to start the comparison operation when both count values accord with each other; and a fifth comparison means for detecting whether the count value of the second counter accords with the fourth count value stored in the fourth count value storing means and for enabling said first comparison means to stop the comparison operation when both count values accord with each other.

Claim 9

The synchronizing signal reading apparatus according to claim 6, wherein said comparing means enables said selection means to select the fifth count value stored in said fifth count value storing means when said count value of the third counter accords with the sixth count value.

Claim 10

The synchronizing signal reading apparatus according to claim 8, wherein said comparing means enables said selection means to select the fifth count value stored in said fifth count value storing means when said count value of the third counter accords with the sixth count value.

Claim 11

The synchronizing signal reading apparatus according to claim 2, wherein said synchronizing pattern detecting means and said synchronizing pattern detecting judging means comprise a synchronizing pattern data storing means for storing said synchronizing pattern data; a second reading data storing means for storing the serial data having the same bit number as the latest synchronizing pattern data read from said recording medium; a seventh comparing means for comparing the data stored in said synchronizing pattern data storing means with the data stored in the second data storing means; and a third effective time period setting means for setting the third effective time period in which said seventh comparing means performs the comparison.

Claim 12

The synchronizing signal reading apparatus according to claim 11, wherein, said first effective time setting means and said third effective time setting means comprises: storing means for storing the seventh count value designating a start of the third effective time, the eighth count value designating a completion of the third effective time, the ninth count value designating a start of the first effective time and the tenth count value designating completion of the first effective time; read control means for performing a control so that the seventh count value, the eight count value, the ninth count value and the tenth count value are stored in said storing means and output therefrom in this order; the fourth counter for performing a count operation in synchronization with a clock of the fourth frequency; detecting means for detecting whether the count value of the fourth counter coincides with the count value output from said storing means; and means for providing an instruction such that, when said detecting means detects that the count value of the fourth counter coincides with the seventh counter value, the seventh comparison means starts a comparison operation; when said detecting means detects that the counter value of the fourth counter coincides with the eighth count value, said seventh comparison means stops the comparison operation; when said detecting means detects that the count value of the fourth counter coincides with the ninth count value, said first comparison means starts the comparison operation; and when said detecting means detects that the count value of the fourth counter coincides with the tenth count value, the first comparison means stops the comparison operation.