Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1999-11-01
2001-11-13
Peikari, B. James (Department: 2186)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C710S030000, C710S034000, C710S057000, C710S065000, C710S068000
Reexamination Certificate
active
06317809
ABSTRACT:
U.S. Pat. No. 5,185,732, Ogawa et al., is incorporated for its showing of the prior art format of optical disk data sectors which are stored in a continuous sequence.
TECHNICAL FIELD
This invention relates to the storage of data in a continuous sequence of sectors, and more particularly to the protection against under-run of the data being organized in a buffer for storage in sectors or blocks of data.
BACKGROUND OF THE INVENTION
Optical disk media typically comprise a continuous spiral groove which extends for the entire data storage capacity of the disk. CD-based (CD-R or DVD-R) optical disk media architecture utilizes the continuous spiral groove with sectors (also called “blocks”) of equal length, which are accessed at a constant linear velocity (CLV). Thus, there are a greater number of sectors along the outer tracks of the spiral than at the inner tracks of the spiral.
Herein, the terms “block” and “sector” are used interchangeably.
The CD-R (CD-recordable) optical disk media is CD-based and comprises a continuous spiral CLV media. The coding modulation for CD-R is called “EFM”, which means eight-to-fourteen modulation. The encoding turns the input data, along with error correction data, address information, synchronization patterns, and other miscellaneous content, into an encoded binary stream of bits, expanding every eight bits of input data into fourteen, with an additional three bits to separate words, as is well known in the art. In the CD-R format, 24 of the resultant 17 bit symbols are assembled into a frame. 98 frames are grouped together to form a sector. A layered level of error correction is accomplished on a “diamond” or combined lateral and slant pattern across the frames to avoid the total loss of a frame of data, as is known in the art. Thus, each sector comprises a totality of 98 frames of data, together with a sector header, synch information and layered ECC distributed across the frames and sectors. The CD-R media does not provide molded sector or block identification marks to identify data recording positions. The sectors are therefore formatted with headers having a great deal of information to aid in synchronizing the rotation of the disk and obtaining data framing, comprising a great deal of overhead. A limited number of entries may be placed in the table of contents on the disk for locating the beginning of recorded areas. Therefore, it is very important for CD-R to not interrupt the data writing process because of this overhead penalty.
Current CD-R devices therefore have a buffer to accumulate the input data to organize the data into sectors for writing on the disk in a continuous sequence of sectors.
When the current buffer of a CD-R device fails to receive input data from the host on a timely basis (due to higher priority tasks or interrupts using host resources), the buffer may under-run and will become empty, causing the writing process to be halted in an orderly fashion, resulting in a data file being partially written. One proposed solution, which is undesirable, is to stop writing sectors upon the occurrence of the under-run. This is because in CD-R devices, it is not possible to restart the writing process without incurring the space and table of contents overhead, and it results in a disk having the appearance of two-recorded files. Most often, the user application cannot deal with the complexity or with the two data files where one is expected, so the disk is considered ruined and discarded.
What is needed is a means for protecting the recording of the optical disk against under-run of the input data to the buffer.
SUMMARY OF THE INVENTION
In an optical data storage device for storing data on a removable optical disk in a continuous sequence of sectors, having a buffer for buffering the input data, which buffer may be subject to under-run, under-run protection is provided by an under-run detector responsive to the buffered data comprising less than a sector of data for indicating an under-run, and a padding provider responsive to the under-run indication for providing padding signals for formatting into sectors. The sectors may be provided with headers indicating the sectors as padding. A reading device for reading the data sectors and providing the data to a host detects padding data and prevents the padding data from being transmitted to the host.
For a fuller understanding of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.
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Kulakowski John Edward
Means Rodney Jerome
Winarski Daniel James
Holcombe John H.
International Business Machines - Corporation
Peikari B. James
Sullivan Robert M.
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