Apparatus for selectively comparing pointers to detect full or empty status of a circular buffer area in an input/output (I/O) buffer

• US 5,537,552 A
• Filed: 08/17/1993
• Issued: 07/16/1996
• Est. Priority Date: 11/27/1990
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ogino, Yoshitaka, Ogasawara, Yutaka, Shimakura, Masami
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): BARRY, LANCE LEONARD
• Application Number:
  US08/093,039
• Time in Patent Office: 1,064 Days
• Field of Search: 360/27, 364/DIG. 1, 364/DIG. 2, 365/73, 365/189.04, 365/189.05, 365/74, 395/250, 395/275, 395/425, 395/800, 395/200.08, 395/872, 395/876, 395/877, 395/405, 395/457, 395/464, 395/419, 395/421.03, 395/375
• US Class Current: 710/57
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0656 Data buffering arrangements
• CPC Class Codes: G06F 5/14 for overflow or underflow handling, e.g. full or empty flags

Abstract

An information reproducing apparatus for reproducing recorded data includes a buffer, a control device and a determining device. The buffer stores data blocks read out from a recording medium and includes first and second storage areas having respectively discontinuous storing and read addresses. The apparatus is controlled to execute in parallel a first process for storing the data blocks into the buffer and a second process for reading out the data blocks stored in the buffer to transfer the data blocks to a host apparatus. The determining device determines whether there are data in the first storage area to be transferred to the host apparatus by comparing a storing address in the buffer of the data which are being stored into the first storage area with a read address in the buffer of the data which are being read out from the first storage area. The first process is controlled so that a predetermined data block which has been read out from the recording medium is stored into the second storage area. When the predetermined data block is stored into the second storage area, the determining device does not compare the storing address in the buffer of the data which are being stored into the second storage area with the read address in the buffer of the data which are being read out from the buffer.

Claims

1. An information reproducing apparatus for reproducing data recorded on a recording medium, said apparatus comprising:

input means for inputting data read out from data blocks of the recording medium;

a buffer for storing data input by said input means, said buffer having a first storage area and a second storage area, said first storage area storing data of normal data blocks input by said input means and being a ring buffer in which data storing is restarted from a head address when the data storing at an end address is completed, and said second storage area storing data of specific data blocks input by said input means;

transfer means for transferring the data stored in said buffer to a host apparatus;

control means for controlling said apparatus to execute in parallel a first process for storing data into one of the first storage area and the second storage area in said buffer and a second process for reading out data stored in one of the first storage area and the second storage area in said buffer to transfer data to the host apparatus by said transfer means; and

determining means for determining whether there are data in the first storage area to be transferred to the host apparatus by comparing a storing address in said buffer of the data which are being stored into the first storage area with a read address in said buffer of the data which are being read out from the first storage area, when said control means reads out the data already stored in the first storage area while storing the data of the normal data blocks into the first storage area,

wherein said determining means does not compare the storing address in said buffer of the data which are being stored into said second storage area with the read address in said buffer of the data which are being read out from the first storage area, when said control means reads out the data already stored in the first storage area while storing the data of the specific data blocks into the second storage area.

2. An apparatus according to claim 1, wherein when the data of the specific data block are stored into the second storage area in the buffer, said determining means determines whether there are data in the first storage area to be transferred to the host apparatus by comparing the last storing address in said buffer of the data which have been stored into the first storage area in said buffer just prior to storing the data of the specific data block with the read address in said buffer of the data which are being read out from the first storage area.

3. An apparatus according to claim 1, wherein when said determining means determines that no data in the buffer are to be transferred to the host apparatus, said control means temporarily interrupts the transferring of data to the host apparatus.

4. An information reproducing apparatus for transferring data which have been read out from a recording medium to a host apparatus, said apparatus comprising:

input means for inputting data read out from data blocks of the recording medium;

a buffer for storing data input by said input means, said buffer having a first storage area and a second storage area, said first storage area storing data of normal data blocks input by said input means and being a ring buffer in which data storing is restarted from a head address when the data storing at an end address is completed, and said second storage area storing data of specific data blocks input by said input means;

transfer means for transferring the data stored in said buffer to a host apparatus;

preread control means for controlling said apparatus to read out data of a next data block of a data block whose transfer to the host apparatus has been designated, subsequent to the reading of data of the designated data block;

storage control means for controlling said apparatus to store data of the designated data block into said first storage area in said buffer and data of the next data block of the designated data block into said second storage area in said buffer;

control means for controlling said apparatus to execute in parallel a first process for storing the data into one of the first storage area and the second storage area in said buffer and a second process for reading out the data from one of the first storage area and the second storage area in said buffer to transfer data to the host apparatus by said transfer means; and

determining means for determining whether there are data in the first storage area to be transferred to the host apparatus by comparing a storing address in said buffer of the data which are being stored into the first storage area with a read address of the data which are being read out from the first storage area, when said control means reads out the data already stored in the first storage area while storing the data of the normal data blocks into the first storage area,

wherein said determining means does not compare the storing address in said buffer of the data which are being stored in the second storage area with the read address in said buffer of the data which are being read out from the first storage area, when said control means reads out the data already stored in the first storage area while storing the data of the specific data blocks into the second storage area.

5. An apparatus according to claim 4, wherein during the storage of the data into the second storage area in the buffer, said determining means determines whether there are data in the first storage area to be transferred to the host apparatus by comparing the storing address in said buffer of the data which were last stored into the first storage area with the read address in said buffer of the data which are being read out from the first storage area.

6. An apparatus according to claim 4, wherein after data of the designated data block has been transferred to the host apparatus, and when there is an instruction for transferring data of the next data block of the designated data block, data of the next data block is read out from the second storage area and transferred to the host apparatus without reading out data of the next data block from the recording medium.

7. An apparatus according to claim 4, wherein when said determining means determines that there are no data in the first storage area to be transferred to the host apparatus, the control means temporarily interrupts the transferring process.

8. An information reproducing apparatus for reproducing data recorded on a recording medium, said apparatus comprising:

input means for inputting data read out from data blocks of the recording medium;

a buffer for storing data input by said input means, said buffer having a first storage area and a second storage area, said first storage area storing data of normal data blocks input by said input means and being a ring buffer in which data storing is restarted from a head address when the data storing at an end address is completed, and said second storage area storing data of specific data blocks input by said input means;

transfer means for transferring the data stored in said buffer to a host apparatus;

control means for controlling said apparatus to execute in parallel a first process for storing data into one of the first storage area and the second storage area in said buffer and a second process for reading out data stored in one of the first storage area and the second storage area in said buffer to transfer data to the host apparatus by said transfer means; and

determining means for determining whether an amount of data in the buffer which have not yet been transferred to the host apparatus, is equal to a predetermined amount by comparing a storing address in said buffer of the data which are being stored in the first storage area with a read address in said buffer of the data which are being read out from first storage area, when said control means reads out the data already stored in the first storage area while storing the data of the normal data blocks into the first storage area,

wherein said determining means does not compare the storing address in said buffer of the data which are being stored into the first storage area with the read address in said buffer of the data which are being read out from the second storage area, when said control means reads out the data already stored in the second storage area while storing the data of the normal data blocks into the first storage area.

9. An apparatus according to claim 8, wherein when the data stored in the second storage area in the buffer are transferred to the host apparatus, said determining means determines whether an amount of data in the buffer which have not yet been transferred to the host apparatus is equal to a predetermined amount by comparing the read address in said buffer of the data which have been read out from the first storage area just prior to reading out the data from the second storage area with the storage address in said buffer of the data which are being stored into the first storage area.

10. An apparatus according to claim 8, wherein when said determining means determines that the amount of data in the first storage area in said buffer which have not yet been transferred to the host apparatus is equal to the predetermined amount, said control means temporarily interrupts the storage of the data into the first storage area in the buffer.

11. An information reproducing apparatus for transferring data which have been read out from a recording medium to a host apparatus, said apparatus comprising:

input means for inputting data read out from data blocks of the recording medium;

a buffer for storing data input by said input means, said buffer having a first storage area and a second storage area, said first storage area storing data of normal data blocks input by said input means and being a ring buffer in which data storing is restarted from a head address when the data storing at an end address is completed, and said second storage area storing data of specific data blocks input by said input means;

transfer means for transferring the data stored in said buffer the host apparatus;

preread control means for controlling said apparatus to read out data of a next data block whose transfer to the host apparatus has been designated, subsequent to the reading of data of the designated data block;

storage control means for controlling said apparatus to store data of the designated data block into the first storage area in said buffer and data of the next data block of the designated data block into the second storage area in said buffer;

control means for controlling said apparatus to execute in parallel a first process for storing the data into one of the first storage area and the second storage area in said buffer and a second process for reading out the data from one of the first storage area and the second storage area in said buffer to transfer the data to the host apparatus by said transfer means; and

determining means for determining whether an amount of data in the first storage area in said buffer which have not yet been transferred to the host apparatus is equal to a predetermined amount by comparing a storing address in said buffer of the data which are being stored into the first storage area with a read address in said buffer of the data which are being read out from first storage area, when said control means reads out the data already stored in the first storage area while storing the data of the normal data blocks into the first storage area,

wherein said determining means does not compare the storing address in said buffer of the data which are being stored into the first storage area with the read address in said buffer of the data which are being read out from the second storage area, when said control means reads out the data already stored in the second storage area while storing the data of the normal data blocks into the first storage area.

12. An apparatus according to claim 11, wherein when the data are being read out of the second storage area in the buffer, said determining means determines whether the amount of data in the first storage area which have not yet been transferred to the host apparatus is equal to the predetermined amount by comparing the read address in said buffer of the data which were last read out from the first storage area with the storing address in said buffer of the data which are being stored.

13. An apparatus according to claim 11, wherein when said determining means determines that the amount of data in the first storage area in said buffer which have not yet been transferred to the host apparatus is equal to the predetermined amount, said control means temporarily interrupts the storage of the data into the first storage area in said buffer.