WO1992021224A2

WO1992021224A2 - Optical disk drive assembly having selectable compression and emulation

Info

Publication number: WO1992021224A2
Application number: PCT/US1992/004534
Authority: WO
Inventors: Richard A. Jorgensen
Original assignee: Maxoptix Corporation
Priority date: 1991-05-29
Filing date: 1992-05-28
Publication date: 1992-12-10
Also published as: WO1992021224A3; AU2177592A

Abstract

A system is disclosed for storing data on, and receiving data from, an optical disk. The data may be provided by a host computer. A compression/decompression circuit is included, and the data may be compressed or uncompressed in this circuit, at the option of a user, who can select from compression modes including a bypass mode and a target ratio mode. A converter circuit is included for translating from the host computer's commands to the optical disk drive's commands. The user may select a specific emulation for compatibility with other disk systems, and the user may select specific setup parameters for compatibility with a variety of host computers. Process control circuitry operates the compression and decompression circuit in one of a number of modes and emulations. The system may be enclosed in a full form factor size package. A display and manual controls, accessible to a user, are provided for user interface with the system. Many user options are provided to enhance compatibility with a wide variety of disk systems. The present invention provides a large storage capability for storing large amounts of information in less physical space. The system of the present invention is suitable for ''plug and play'' installation by computer manufacturers. As an additional advantage, the user can easily monitor data compression with the display that shows the compression ratio, continuously updated.

Description

OPTICAL DISK DRIVE ASSEMBLY HAVING SELECTABLE COMPRESSION AND EMULATION

BACKGROUND OF THE INVENTION

FIELD OF INVENTION

The present invention relates to optical disk drives for storage of digital information. More specifically, the present invention relates to a system including an optical disk drive and associated circuitry for data compression and conversion of commands, with a capability for selection of the compression mode, emulation of a number of pre-existing systems and selection of setup parameters. The system of the present invention may be enclosed in a housing with a size corresponding to the industry's 5.25" full height form factor standard, with manual controls for mode, emulation, and setup selection.

DESCRIPTION OF RELATED ART

The capability for storage of digital data has expanded dramatically over the past twenty years. Digital information was first stored on reels of magnetic recording tape; however, this storage method proved cumbersome, access to data was slow, and required many large reels of tape. The advent of the floppy disk ushered in a new era of speed and information density for digital storage. Over the past few years, new products, such as the hard disk drive (often called the Winchester drive) have evolved, so that at present, storage capacities of 40 MB or more are common in hard disks internal to many personal computers, and access to much of the data is very quick.

Much greater storage capacities are possible in optical disks; for example, the Maxoptix® RXT-800HS, available from Maxoptix® Corporation of San Jose, CA, the assignee herein, can store 786 Megabytes of information on a write once optical disk. The Maxoptix^® RXT-800HS drive is available in a half-height housing. Optical drives typically allow writing only once, and are often called "WORM" drives (for write-once, read-many). Erasable optical drives are also available.

An optical disk is inserted into the disk drive for writing or reading, and the disk can be removed for archival purposes. As a space saving media, optical disks are attractive for many uses, particularly when large amounts of data must be stored. Examples of optical disks include compact disks (CDs) used for digital music recording. Other uses for optical disks includes library storage of information such as images, databases, spreadsheets, desk-top publishing, CAD files, programs, binary data, and word processing. Optical disks are useful as backup storage media for computer networks having one or more disk drives. Massive storage capabilities are useful in medical processes that produce a large amount of digital data. For example, imaging processes, such as MRI (Magnetic Resonance Imaging), output large quantities of data that must be stored quickly and efficiently. Later, when time is available , the data is processed to provide images useful for diagnosis and surgery. As discussed, optical disks are useful for storage of large amounts of information. However, it would be an advantage to provide an even greater storage capability than that provided by the existing optical disk systems. To increase storage capacity of other non-optical digital recording formats such as hard disks, data compression circuitry has been used. For example, a data compression chip, the #9703 data compression co-processor, is available from Stac Electronics, of Carlsbad, California. However, data compression has not been used with optical disk drives in any meaningful way; one so-called data "compression" system for optical disk drives provides almost negligible storage reduction (0-5%) by using simple software driven routines. For example, if this system sees a string of blanks (zeros), it simply skips the data, effectively throwing it away. To significantly and meaningfully increase storage abilities, it would be an advantage to provide a compression system for an optical disk drive that can compress data two or more times. For example, with a 3:1 compression ratio, a 786 Megabyte drive can store 2.35 Gigabytes of information. Another problem with data compression, as applied to optical disk systems, is the lack of compatibility between disks recorded without compression, and disks recorded with compression. Furthermore, whether or not disks are recorded with compression, optical disks are not fully portable between systems. In other words, an optical disk written with one system may not be usable by another. It would be an advantage to provide an optical disk system that can compress data for greater storage density, while having a capability for emulating any of a number of pre-existing disk drives, so that the system would be compatible with optical disks recorded by those pre-existing systems. Also, it would be an advantage if a user could select the emulation parameters and the compression mode. It would be a further advantage if the user could select the emulation and compression manually from the optical disk drive housing, without accessing a computer.

In the computer industry, great effort has been expended to provide faster, more powerful computers in smaller, compact, marketable packages. This effort has lead to the development of de facto standards that enhance compatibility between products of different manufacturers. Standards have developed for communications between computers and Winchester hard disks; most present-day computers are designed with an ability for communication with a Winchester hard disk. This communications ability is embodied in both software and hardware.

Further, de facto standards include the housing size of disk drives; many large computer manufacturers follow the industry's standards, and have allotted an internal space the size of a standardized "full height form factor" for their 5.25" disk drives. This full height housing size is available from a number of OEM manufacturers of disk drives; thus, any of these OEM manufacturers' drives can be installed successfully.

Because the space for a full height housing has already been allotted by many manufacturers, it would be an advantage if an optical disk drive were available in a full height form factor package, and it would be a further advantage if the package were compatible with the Winchester drive communication links that are standard in most computers. As stated above, write once optical disk drives are available in the half height form factor size. However, these drives inherently have different communication requirements than the Winchester drives. In order to achieve compatibility with this type of optical drive, the computer must be re-programmed with a software driver that converts to the appropriate commands for interfacing with the optical disk drive. However, software-based conversion is relatively slow, and far greater speeds are possible by using an available hardware-based conversion circuit. An example of a conversion circuit containing hardware specifically designed to perform the conversion at high speed is the Optical Conversion

Unit (OCU™) available from Ten X Technology Corporation of Austin, Texas. The OCU™ acts as an interface to connect the Winchester communications systems with the optical disk drive. In one configuration, the OCU™ is available in a half height form factor package. A front panel display is provided that supports entry of data at initialization and displays information about the operation of the unit. If a full form package were available, it would be a further advantage if it included data compression circuitry for increasing the data storage capacity, and if the data compression could be controlled from the front panel for effective and convenient user interface.

It would be an additional advantage if the system contained error detection and correction circuitry to ensure that the compressed data is written correctly to the disk, and that the data is read correctly from the disk. It would also be an advantage if errors were corrected in the instance when the data is incorrectly read from the disk. It would be an even further advantage if the error correction were provided after data compression during a write, and before data decompression during a read.

SUMMARY OF THE INVENTION

The system of the present invention provides an optical disk drive system that includes data compression to achieve storage capacities much greater than previously available. In addition, the compression mode and the emulation parameters can be selected to achieve compatibility with a large number of pre-existing optical disks and optical disk systems. The user can also select setup parameters in order to achieve compatibility with a variety of host computers. A number of preset selections (presets) are available for the user to select, in a single stroke, the setup parameters for some common host computers. The system can be enclosed in a standard size housing, the industry's 5.25" full height form factor size, that is easily installed in most standard computers. Furthermore, the system is compatible with most hard drive communication capabilities provided by standard computers.

The present invention provides a system for storing data on, and receiving data from, an optical disk. The data may be produced by a host computer or any other appropriate digital device. The system of the present invention comprises an optical disk drive sub-assembly and a circuit for compressing data transmitted into the sub-assembly, and for decompressing data transmitted from the sub-assembly. The compression/decompression circuit communicates with the optical disk drive sub-assembly via a standard communications bus that transmits data between the optical disk drive sub- assembly and the compression/decompression circuit. Control circuitry is provided for operating the compression/decompression circuit in any of a number of available compression modes and emulations. In one compression mode, the compression/decompression circuit is activated and operates to compress or decompress the data as much as possible within its capabilities. In another mode, a "bypass" mode, the compression/decompression circuit is de-activated (bypassed) so that no compression or decompression occurs. In still another mode, a "target ratio" mode, a target compression ratio is selected before a writing operation. The target ratio may be selected from a number of available options. During operation, the compression/decompression circuit is controlled so that compression occurs only if the target ratio is attainable; if the target ratio is not attainable, then the compression circuit is bypassed and the data is written in its uncompressed form. In the writing process, the existence of compression is associated with each partition block of data on the optical disk by writing this information to the optical disk. Thus, when the data is to be read, the existence of data compression is first determined by reading this information from the disk, and then the process control circuit accordingly either bypasses or sets the decompression. Some compression modes may be used with specific emulations of other optical disk drives. The compression modes may be selected by user manipulation of manual controls such as buttons electrically connected to the system's selection circuitry. Similarly, the emulations for the hard disk may be selected by the buttons. Also the setup parameters can be selected by the buttons, in order to provide flexibility for interfacing with any of a variety of computers. A number of preset selections (presets) are available for the user to select, in a single stroke, the setup parameters for some common computers. Alternately, the modes, emulations, and setup parameters may be selected through the computer's interface with the system's circuitry. When the system is positioned in a housing, the modes, emulations, and setup parameters may be selected by manual controls accessible from outside the housing. A front panel on the housing may include a front panel having a display viewable by a user, and buttons accessible to a user.

The system of present invention includes a conversion circuit for converting commands to be compatible with any of a number of standard computers. Most standard computers include a SCSI bus that provides disk drive commands for controlling random access disks, such as the Winchester hard disk that can be written over. However, an optical disk drive sub-assembly during writing is responsive to commands suitable for a sequential access disk, and a WORM (write-once, read-many) disk is not rewriteable. During reading, the optical disk can be accessed randomly, but access requires use of a directory built previously during sequential recording. Furthermore, the size of the basic storage units are different; a hard drive generally has sector sizes of 512 or 1024 bytes while an optical drive may have larger sector sizes ranging from 512 to 4096 bytes, including 512, 1024, 2048, and 4096 bytes.

On the front panel of the housing, the display can show the emulation selected, as well as other information relating to the optical disk such as the amount of storage remaining available for recording. During writing operations, the display may be selected to show the average compression ratio, or the free space, updated continuously. During reading operations, the display may be selected to show the average compression ratio attained when the data was written to the disk. Positioned on the front panel, buttons may be provided for user selection of the emulation and other user requirements. For example, the controller may be operated in a "bypass" mode wherein the data compression stage is bypassed in order to read disks previously recorded without data compression. The display and the selection buttons may also allow direct selection of data compression parameters such as the target ratio of data compression; for example, the user may choose from several target ratios. In other embodiments, the computer may select the data compression parameters and the type of emulation. For avoidance of errors, _ parity checks are provided at communication links. Error correction circuitry is provided to correct errors occurring during writing to the optical disk, and reading from the optical disk. The present invention provides several advantages. One advantage is the large storage capability, and another related advantage is the savings in computer time. Optical disks are useful in archiving, or storing large amounts of information. Information stored in its compressed form occupies much less physical space on a disk, and writing and reading compressed data takes much less time than writing uncompressed data. This means that, to store a given amount of information, fewer disks are necessary, and less computer time (and operator time, as well) is used up. Fewer disks means less cost and less time for an operator who must wait, and insert and remove disks during writing and reading operations. For example, a 10:1 compression ratio can increase disk capacity by ten times, saving the cost of ten separate disks, and reducing expensive time spent by the computer and the operator by as much as a factor of ten.

As an additional advantage, the user has suostantial control over the writing process. During writing operations, the display shows the compression ratio updated continuously; because the compression ratio varies dependent upon the data to be compressed, this information may be beneficial to a user.

Before writing, a user may select the type of emulation, the data compression mode, and the setup parameters by manual control using the buttons positioned on the front panel. Thus, for ,. compatibility with a number of different computers and optical disk systems, the setup parameters, compression mode, and emulation can be selected easily. As an example, disks previously recorded by the RXT-800HS can be read in the "bypass" mode, wherein the data compression step is bypassed. For additional flexibility in application, the computer can issue emulation commands directly to the controller through the SCSI bus, so that the emulation or the compression ratio can be adjusted automatically, if desired, without manual selection. Furthermore, selection of a specific data compression mode may- have additional advantages to a user. For example, if data to be written has been previously compressed, then that data should not be compressed further. In that instance, the user may select the bypass mode so that the data bypasses the compression process. As another example, a user may wish to completely bypass the compression process for one reason or another, and therefore this user would choose the bypass mode even though compression is available to him.

As an additional feature, the user can select the termination of the communications buses remotely, from the front panel. This feature provides an advantage in convenience for the user who, if he had followed conventional methods, would directly connect a jumper wire to make the termination. Using the selectable termination option, the user can easily choose to terminate the communications bus as appropriate, without using jumper wires.

As another advantage, the compression/decompression circuit interfaces better with the optical disk's larger sector size than with the smaller sector size of a hard disk. A standard hard disk has a sector size of 512 bytes, while an optical disk can, and typically does, have a larger sector size, such as 2048 bytes, or even 4096 bytes. The compression/decompression circuit functions well with a boundary of 4096 bytes, which can be obtained directly from a sector size of 4096 bytes, or can be obtained if 2-2048 byte sectors are combined. In comparison to obtain 4096 bytes in a hard disk format requires that eight 512 byte sectors be combined. As an additional advantage, in the optical disk, the relatively fewer number of large size sectors (2) provides better storage control, and simplified and faster storage operations. Furthermore, a larger sector size makes more efficient use of the disk storage space. By using larger sectors, more data can be stored on the disk in a continous string; the boundaries are larger, and less space is used recording the boundaries and other file information.

The compression ratio will vary widely, dependent upon the data; data such as programs may compress at a ratio around 2.5, but other data such as black and white images may compress at a ratio around 20. At the present time, compression ratios of up to 29:1 have been observed for black and white pixel images

(grey scale).

As a further advantage, the system of the present invention is suitable for "plug and play" installation by computer -. manufacturers. Particularly easy installation in a wide variety of computers is afforded when the system is packaged in a full height form factor housing. The form factor standards are followed by most computer manufacturers, and thus this housing can be easily installed in pre-existing computer slots. Additionally, most computers are designed to operate a Winchester hard drive. The conversion circuit can make the optical disk emulate a hard drive, thus providing compatibility with a wide variety of computers.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is diagrammatic illustration of a system for writing to, and reading from, an optical disk.

Figure 2 is a perspective view of a full height form factor housing for the writing/reading system, including a front panel having a display and manual buttons, the housing being suitable for installation in a computer.

Figure 3 is a perspective view of a housing for the reading/writing system, positioned in a computer with the housing's front panel facing outward and accessible to a user. Figure 4 is a block diagram of a system for writing to, and reading from, an optical disk, illustrating more detail than Figure 1 .

Figure 5 is a flow chart illustrating operation during a data-in process wherein data from a computer is compressed and written to an optical disk.

Figure 6 is a flow chart illustrating operation during a data-out process wherein data is read from the optical disk, decompressed, and transmitted to the computer.

Figure 7 depicts a series of displays that are shown on the front panel LCD display in a preferred embodiment.

Figure 8 depicts a series of options available to a user in a preferred embodiment.

Figure 9 is a table that shows the available compression modes and emulations in a preferred embodiment. Figure 10 is a table that shows preset configurations for setup parameters in the preferred embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The invention is best understood by reference to the figures wherein like parts are designated with like numerals throughout.

Reference is made to Figure 1 , which illustrates, in block diagram form, a system for storing data on, and receiving data from, an optical disk. Figure 4, in comparison, is a block diagram that illustrates additional features, and these more specific features are described with reference thereto. Referring back to Figure 1 , a host computer 10, or another appropriate digital device, originates appropriate data and commands, which are transmitted to a controller 12. The controller 12 may respond with its own data and commands, which are transmitted back to the host computer 10. The controller 12 includes a compression/decompression circuit 13 that can compress data transmitted from the host computer 10. The compressed data is transmitted to an optical disk drive sub-assembly 14 along a data link 16. The optical disk drive sub-assembly 14 is a commercially available package that includes an optical disk drive unit and associated electronics described later with reference to Figure 4. In a write of compressed data to the disk sub-assembly 14, the data link 16 transmits compressed data to the sub-assembly 14. In a read of compressed data from the sub- - assembly 14, the data link 16 transmits compressed data to the compression/decompression circuit 13, which decompresses the data. Thus, the inputted compression/decompression circuit 13 compresses data which is to be transmitted into the sub- assembly 14, and it decompresses data transmitted from the sub- assembly 14. The controller 12 also includes a process control circuit 17, which can control operation in one of a number of available modes of operation of the compression/decompression circuit 13, as well as provide a specific emulation by controlling a converter circuit 27 in conjunction with the compression/decompression circuit 13. The process control circuit 17 can also be programmed with setup parameters to provide communications with a variety of host computers 10. The available modes of operation, the emulations, and the setup parameters are discussed more fully with reference to Figures 7, 8, and 9. The particular mode and emulation may be selected by the host computer 10 or the user; i.e., the process control circuit 17 may be responsive to commands from the computer 10, or it may be responsive to commands from manual controls 18 that are accessible to a user. A display 19, such as a LCD display, may provide visual access to information for user verification of parameters and selection of modes. Reference is now made to Figure 2, which illustrates a housing for a system for writing to, and reading from, a optical disk. The system is enclosed in a housing illustrated generally at 20. In the block diagrams of Figure 1 and 4, the system that is included in the housing 20 is shown enclosed within a box also labelled 20. Referring now to Figure 2, a front panel 21 has a slot

22 for inserting and removing a conventional optical disk cartridge (not shown). The front panel 21 also includes an ejection button 23 for ejecting an inserted optical disk. The manual controls 18 are presented on the front panel 23, in a position proximate to the display 19 for ease of user interface. The manual controls 18 include buttons 24,25 for scrolling selections that may be shown on the display 19; specifically, the selection button 24 scrolls up, and the selection button 25 scrolls down. The controller 12 (Figure 1 ) transmits a series of verifications and user options to the display 19 that will be more fully described with reference to Figures 5-8. The manual controls 18 allow the user to move through the series of verifications and select options. One of the user options is selection of the emulation in which the system is operating, so that the user can select the emulation corresponding to the disk that he is inserting for proper reading and writing operations.

Other options include setup parameters, which allow the user to setup the system for operation with any of a variety of computers. For example, the controller 12 may be operated with a RXT-800 emulation to read a disk previously recorded without data compression, using a Macintosh computer as a host. The process control circuit 17 may also allow direct selection of a data compression mode, such as a compression "on" mode, a bypass mode, or a target ratio mode. In some embodiments, the computer 10 may be programmed to select data compression modes, setup parameters, and emulations, either alone or in conjunction with the user. The housing 20, made in the industry's standard full height form factor size, is compatible with any of a number of standard computers. The industry's form factor standards for disk drives are followed by many computer manufacturers. As illustrated in Figure 3, the full height form factor housing 20 is readily inserted in the space available on a PC (personal computer) 26. The industry's standards for the full height form factor are approximately: a depth of 8.00" ± 0.63, a height of 3.25" ± 0.03, and a width of 5.75" ± 0.03. Eight screw holes are provided, four on the bottom, and two on each side. Four of the holes are provided at a distance from the front of 1.87" ± 0.02, and the other four holes are at an additional distance of 3.12" ± 0.02 from the front. The front bottom two holes, spaced evenly from the sides, are separated by a distance of 5.50" ± 0.02. Similarly, the back bottom two holes, spaced evenly from the sides, are separated by a distance of 5.50" ± 0.02. All four side holes are spaced a distance of 0.86" ± 0.02 from the bottom. The screw holes are 6-32 INC x 0.31 deep. Most computers 10, such as the PC 26, are manufactured or programmed with disk drive commands for controlling random access disks, such as the Winchester hard disk. Reference is again made to Figure 1 , particularly the controller circuit 12, „ which includes the converter circuit 27. The converter circuit 27 and the optical disk drive sub-assembly 14 communicate through a command link 28. The converter circuit 27 translates commands from the computer 10 into commands usable by the optical disk drive sub-assembly 14. The optical disk sub- assembly 14 requires commands suitable for a sequential access disk; thus, the converter circuit 27 is designed to quickly and efficiently make the conversion in either direction of command flow. The process control circuit 12 may control the converter circuit 27 as well as the compression/decompression circuit 13, in order to provide control over specific emulations.

Reference is now made to Figure 4, a block diagram more detailed than Figure 1. The host computer 10 includes hardware and software that generates data communications signals 29, which are provided on a computer port 30, and transmitted on a conventional bus 32 to the controller 12. The controller 12 processes the communications signals 29, as will be described, and communicates with the optical disk drive sub-assembly 14 via a bus 38, using communications signals 40. Both the controller 12 and the optical disk drive sub-assembly 14 may be physically positioned within the full height form factor housing 20. In the preferred embodiment, the optical disk drive sub- assembly 14 comprises a RO-5043 drive unit manufactured in

Japan by Ricoh Co., Ltd. with a part number R633-14, and available in the United States from Maxoptix Corporation of San Jose, CA under the trademark RXT-800HS™. The buses 32,38 may comprise any of a number of conventional communication buses; preferably, the buses 32,38 both are constructed in accordance with ANSI standard SCSI CCS-4B, and the communications protocol is in accordance with ANSI standard SCSI-2.

The communications signals 29 provided by the computer 10 may have the form of any of a number of command sets; however, a typical computer 10 is designed to control the

Winchester hard disk drive, and thus the communications signals 29 may comprise instructions for a Winchester hard drive, a random access disk. To differentiate the two sets of instructions for purposes of explanation, the instruction set by which the computer 10 communicates with the controller 12 will be referred to as the computer command set, and the optical drive command set refers to the command set by which the optical disk drive sub-assembly 14 communicates with the controller 12. The optical disk drive sub-assembly 14 is a sequential access unit, and therefore the optical drive command set will typically be different than the computer command set which is designed for random access.

The communications signals 29 are transmitted to a buffer 42, preferably having a 2x4K dual ported configuration, and are stored therein until needed by a microprocessor 44. A selectable termination network 43 is positioned between the bus 32 and the buffer 42, and it is controlled by the microprocessor 44. The selectable termination network 43 may include a conventional network such as parallel resistors controlled by a single transistor. When the transistor is switched "on" by the microprocessor 44, a current path through the resistors is provided to ground, thereby terminating the communications bus. The termination network 43 is provided to reduce noise on the bus 32. Preferably, the microprocessor 44 comprises a NEC V50, although other microprocessors may be suitable. The microprocessor 44 is programmed to perform several functions, including conversion of the computer instruction set into the drive unit instruction set usable by the optical disk drive sub- assembly 14. Another function of the microprocessor 44 is control of the mode of operation such as the compression ratio and the emulation; thus in this embodiment, the microprocessor

44 includes the process control circuit 17 (Figure 1 ). The microprocessor 44 is also programmed to control the display 19 that may comprise a standard LCD (Liquid Crystal Display) for user viewing. The manual controls 18 may include a plurality of buttons for user control of the microprocessor 44. The functions of the buttons, and the information appearing on the display 19 are discussed in detail with reference to Figures 5-10; generally, it can be said here that the microprocessor 44 is programmed to display a series of verifications and queries, to which the user may respond, as appropriate, by selectively pushing the buttons.

In addition, a port 45 is provided so that a terminal 46 directly accesses the microprocessor 44. For example, the terminal 46 can monitor the microprocessor's state or program its operations. The terminal 46 includes a keyboard and a monitor, and appropriate communication circuits. The terminal 46 is particularly useful in diagnostic testing. The terminal 46 may be included in a computer.

The microprocessor 44 is also connected to the compression/decompression circuit 13, that preferably comprises a data compression chip, the #9703 Data Compression

Co-processor, available from Stac Electronics of Carlsbad, California. The microprocessor 44, in addition to being programmed for conversion between the computer's command set and the optical drive's command set, is programmed to control the compression mode; for example, the microprocessor 44 can control the compression "on" mode, the bypass (compression "off") mode, and the target ratio mode, in response to user selection of the manual controls 18. A pre-buffer 52 is connected between the microprocessor 44 and the compression/decompression circuit 13 in order to temporarily store data passed between the microprocessor 44 and the circuit 13. An additional buffer 54 is positioned between the compression/decompression circuit 13 and the communications bus 38, in order to store data and instructions as needed to compensate for a difference in flow rates. Preferably, the buffer 54 has a 2x60K dual ported configuration.

The microprocessor 44 can calculate an average compression or decompression ratio by comparing the amount of input data to the compression/decompression circuit 13 with the amount of output data. Specifically, by comparing the amount of data input from the pre-buffer 52 to the compression/decompression circuit 13 with the amount of data output from the compression/decompression circuit 13 to the buffer 54, an average compression ratio can be calculated. The average compression ratio is available to be shown in the LCD display 19 during a write or a read. In the case of a write, the data's average compression ratio is that being attained in the ongoing compression process. In the case of a read, the data's average decompression ratio corresponds to the compression ratio that had been attained during the prior writing of the data to the disk.

At its connection to the bus 38, the optical disk drive sub-assembly 14 comprises a communications controller 58, based on the SCSI standards that controls the flow of data along the bus 38. The communications controller 58 is connected to a standard disk controller device 60 that controls optical electronics 62 and servo electronics 64. The optical electronics are connected to a optical head 65, which includes a laser diode and a lens. Thus, reading and writing operations to a disk 66 are controlled by the disk controller 60, via the optical electronics 62, the servo electronics 64, and the optical head 65. The sectors on the optical disk 66 have a size of 2048 bytes. Because the compression/decompression circuit 13 operates best within a 4K boundary, the boundaries are set to be 2 sectors (4096 bytes). An internal, large buffer 68 is connected to the communications controller 58 and the disk controller 60. Preferably, the buffer

68 is a dual ported 2x128K buffer, thereby having a total capacity of 256Kbytes. The buffer 68 is provided to store data and instructions as needed to compensate for a difference in flow rates. Furthermore, the buffer 68 temporarily stores information relevant to the directory of the disk 66, including access and location information. Temporary storage in the buffer 68 avoids unnecessarily writing this information to the disk 66 each time the directory is changed. Because the disk 66 can be written only once, each writing corresponds to a disk area that is no longer usable each time the directory is updated. The directory information stored temporarily in the buffer 68 is automatically written to the disk 66 periodically or at the end of the user's session; alternately, at any time during the session, the user may designate that this information be written to the disk 66 by pushing the flush button 69 (Figure 2). A conventional error correction circuit 70 is included in the optical disk drive sub-assembly 14. When data is written to the disk 66, the data is given an appropriate parity, and is re-checked for accuracy. The error correction circuit- 70 then calculates information pertinent to error correction, and then writes this information to the disk 66. When the data is read back, the error correction circuit 70 uses this information to correct errors in the data before it is sent out from the optical disk drive sub-assembly 14.

The flow chart of Figure 5, in conjunction with the block diagram of Figure 4, illustrates the data-in process wherein data is written to the optical disk 66. As illustrated in a box 80, communications signals 29, including commands and data, are generated in the computer 10 and transmitted along the bus 30. As illustrated in a box 82, the signals 29 are input to the buffer 42. Using conventional transmittal procedures, the parity of the signals 29 provided by the computer 10 is checked before it is written to the input buffer 42, and if an error is found, the data is re-sent. Under control of the microprocessor 44, input data is compressed in the compression circuit 13, as illustrated in a box 84, if appropriate to the emulation or compression mode. As illustrated next in a box 86, the compressed data is written to the exit buffer 54, which preferably is a non-volatile type of buffer. The exit buffer 54 may comprise a 2x60K byte dual ported configuration. The buffer 54 accepts data as fast as can be provided by the compression circuit, so that the compression circuit 13 can process continuously without having to wait for its output to clear. Parity of the data exiting the buffer 54 is checked by conventional methods. By comparing the amount of data that is input to the compression circuit 13 with the amount of data that is output from the compression circuit 13, the average compression ratio can be calculated by the microprocessor 44. The exit buffer 54 provides the compressed data on the bus 38, which is transmitted to the optical disk drive sub-assembly 14, as illustrated in a box 88. The large buffer 68 within the optical sub-assembly 14 stores the data until, as illustrated in a box 90, the data can be written to the optical disk

66. The large buffer 68 may include a 2x128K byte dual ported configuration, for maximization of the operational capabilities of the optical head 65. When data is written to the optical disk 66, along with each data block, there is encoded information that is indicative of whether the data stored therein is compressed or not.

The flow chart of Figure 6, together with the block diagram of Figure 4, illustrate the data-out process wherein data is read out from the optical disk 66. As illustrated in the box 100, a request initiated by the computer 10 proceeds through the controller 12 and initiates a request that looks up the directory information. Next, as illustrated in a box 102, the optical disk 66 is accessed at the address requested in the box 100, which accesses data and other file information, such as the information regarding whether or not the data has been compressed. The data read from the optical disk 102 is checked by the error correction circuit 70, in which most errors in data can be detected and then corrected. As illustrated in the next step, a box 104, the read data is then temporarily stored in the large buffer 68, until it can be applied to the buffer 54, as illustrated in a box 106. As the data is transferred to the buffer 54, parity is checked. The buffer

54 operates as a read ahead buffer, and is preferably a non-volatile type of buffer.

The buffer 54 supplies the read data to the circuit 13 that, as illustrated in a box 108, decompresses the data into its standard, uncompressed form, if the data had originally been stored in its compressed form. In the next step, illustrated in a box 110, the decompressed data is applied to the buffer 42, which preferably is a non-volatile type of buffer, and parity is checked upon its exit. Finally, as illustrated in a box 112, the decompressed data is provided on the bus 32, which transmits it to the computer 10.

Figure 7 shows a series of screen displays that appear in the LCD display 19 on the front panel 21 of the housing 20 (shown in Figure 2) in the preferred embodiment. The user is able to scroll through these screen displays with the manual controls 18, shown in Figure 2, by using the up button 24 or the down button

25. If user options are accessible from a particular screen display, then an enter button 116 is used to first access the options, and then the up button 24 or the down button 25 is used to scroll through the options. When selected, the enter button 116 is pushed again and the system returns to the main menu. To exit from a particular option sequence, a cancel button 118 may be pushed.

A first screen display 120 shows the manufacturer's name and system identification. A next display 122 shows the free space available on the optical disk 66. Following that, a screen display 124 allows the user to check the version of the firmware in the device that is running, and a screen display 126 informs the user that the optical disk 66 is initializing the disk -. 66, if the disk is new. Branching from the display 126, the user is able to select a series of options that allow him to set disk parameters for a blank disk to specify the type of disk it will be, such as a high compression disk, a HD disk, or an RXT-800 disk.

Next, in a screen display 128 the user can enable the reserve. The reserve is excess space on the disk that is reserved for writing a directory and file information, and may comprise a substantial amount of storage, such as 5MB. If the user knows that this amount will not be used, then he can select this display and use a portion of the reserve for additional storage. Following that, in a screen display 130, the user selects a method of time stamping for the data. Next, in a screen display 132, the user can verify and select the drive setup. The options available from the drive setup display 132 are shown in Figure 8. Like the screen displays of Figure 7, these options appear in the LCD display 19. As illustrated in Figure 8, beginning at the drive setup display 132, the user can select the setup parameters, the emulation, and the compression mode. In a quick setup option 133, the user can select, in one step, a number of setup parameters that automatically configure the system for communication with several common host computers 10. Typically, a particular type of host computer 10 will require particular setup parameters to be used with the present invention. In the preferred embodiment, a user in one step can select a configuration that includes alPsetup parameters specific to a particular host computer 10. Thus, the user can select one preset configuration from a number preset configurations that may be available, without manually going through the configuration selection process and making the appropriate selections. The preset selection is simpler for the user and avoids the possibility of user errors in configuration selection. For example, an IBM PC may require emulations, reset level, parity, compression levels, and other adjustments set differently than other host computers that can be connected to the assembly of the present invention.

Using the quick setup option 133, the user can select one of the preset options 134,135,136 that correspond to the host computer in a particular system. In the- preset option 134, the user may select the setup parameters for a host IBM PC/AT/MCA. In the preset option 135, the user may select the setup parameters for a host Apple Macintosh computer, and in the preset option 136, the user may select the setup parameters for a host Unix system. Figure 10 shows exemplary setup parameters for the preset options 134,135,136. It will be recognized that other preset options can be added, and that the setup parameters may vary dependent upon the particular host computer 10. If the quick setup option 133 is selected, then the user can avoid selection of the setup parameters provided by the preset options

134,135,136. However, even if the quick setup option 133 is chosen, the SCSI ID must be set for each system, in order to identify the address assigned to the controller 12 by the host computer 10. In an option 137, the user sets the address number of the controller 12 on the SCSI bus 32, if one was not selected in the quick setup option 133. Next, in an option 138, the block size is set by the user so that it corresponds with the block size that the computer 10 expects to see. Even for the same computer, the sector size may differ dependent upon software; for example DOS system 3 has a sector size of 512 bytes, but DOS system 4 may use either 512 or 1024 bytes as a sector size.

In an option 139, an attention option is provided to allow the controller 12 to ignore the removal of a disk 66 from the disk drive. In another option 140, the remaining capacity of the disk, as calculated by the computer without compression is first displayed, and the user may revise this figure to compensate for data compression or for any other reason, which gives a "virtua capacity. In an option 142, the user may set the internal clock. In an option 144, the user may select the type of reset that he wishes to use; in accordance with conventional resets, the choices may be hard or soft. In an option 146, the parity check provided for the SCSI communications can be set on or off. In an option 147, the SCSI termination can be remotely set on or off. In another option 148, the emulation can be selected. For example, as illustrated in the options 150,152,154,155,156,the user may select between emulation of the RXT-HD, RXT-800, the 12" WORM evaluation, XT-8760S, and the generic Winchester, respectively, in an option 158, a user can select the compression mode directly. The option 158 may be associated with specific emulations in the option 148 to prevent selection of compression where it would be incompatible with the emulation. The user can choose between several modes, including a compression "on" mode as illustrated in an option 160 wherein the data is compressed, a bypass mode as illustrated in an option 162, wherein the compression/decompression circuit 13 is bypassed, and a target ratio mode, as illustrated in an option 164, wherein a target compression ratio can be selected. If the target compression ratio is attainable with the data, then it will be compressed as in the compression mode. If the target compression ratio is not attainable, then the compression/decompression circuit 13 will be bypassed as in the bypass mode.

In the compression "on" mode, as an additional feature, the size of the data file is checked after compression and compared with the size of the uncompressed data file. If the compressed data file is larger than the uncompressed data file, then the file is written to the disk without compression. This feature avoids a problem that may occur in the instance that previously compressed data is again compressed. Furthermore, even if the data were not previously compressed, there is no advantage to compressing data if the file size will be larger as a result. For most types of data, a larger compressed size is highly unlikely unless some other problem exists.

Figure 9 is a table that illustrates some possibilities for emulation and compression modes in the preferred embodiment. Specifically, some emulations, such as RXT-800, do not allow a compression mode other than bypass, while other emulations permit the compression on mode and the target ratio mode. In addition, the table shows the type of emulations that are compatible; for example, a disk written in the RXT-HD emulation can be read in the generic Winchester or the XT 8760S emulations. The table shown in Figure 9 is just one example, illustrating the wide possibilities for emulation and compression that are provided by the present invention.

The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiment is to be considered in all respects only as illustrative and not restrictive and the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing descriptions. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

WHAT IS CLAIMED IS:

1. A system for storing data on, and receiving data from, an optical disk, said system comprising: an optical disk drive sub-assembly including input/output means for transmitting data into and out of said 5 sub-assembly; a compression/decompression means, connected to the input/output means of said optical disk drive sub-assembly, for compressing data transmitted into said sub-assembly, and for decompressing data transmitted from said sub-assembly; and 1.0 a process control means for controlling operation of the compression/decompression means so that the compression/decompression means operates in one of a number of available compression modes of operation, said modes including a bypass mode wherein the compression/decompression means is 1 5 bypassed.

2. The system as claimed in Claim 1 , wherein one of said compression modes is a target ratio mode. 3. The system as claimed in Claim 1 , further comprising a means for calculating the average compression ratio, and a display for displaying an average compression ratio during any writing operation to the optical disk.

4. The system as claimed in Claim 1 , further comprising a means for calculating the average compression ratio, and a display for displaying, during read and decompression operations, the average compression ratio, said compression ratio being the compression ratio achieved during a prior writing of the data.

5. The system as claimed in Claim 1 , wherein the process control means further includes means for controlling one of a number of available emulations.

6. The system as claimed in Claim 5, further comprising means for selecting one of the available emulations.

7. The system as claimed in Claim 6, wherein the means for selecting one of the available emulations includes a display viewable by a user, and manual controls accessible to a user.

8. The system as claimed in Claim 6, wherein the means for selecting one of the available emulations includes a port for a terminal, said port being connected to the process control means. 9. The system as claimed in Claim 1 , further comprising a housing for enclosing the optical disk drive unit, the compression/decompression means, and the mode control means.

10. The system as claimed in Claim 9, wherein the housing has a size conforming to the full form factor industry's standard of the computer industry.

11. The system as claimed in Claim 9, further comprising selection means, accessible from outside the housing, for selecting one of said compression modes.

12. The system as claimed in Claim 11 , wherein the selection means comprises a display viewable by a user, and manual controls accessible to a user.

14. A system for storing data on, and receiving data from, an optical disk, said data being provided by a host computer communicating using a computer command set that is incompatible with an optical disk drive command set, said system comprising: an optical disk drive sub-assembly responsive to the optical disk drive command set, said sub-assembly including input/output means for transmitting data into and out of said sub-assembly; and, a controller connected between the computer and the optical disk drive sub-assembly, said controller comprising, a conversion means for converting between the optical disk drive command set and the computer command set, a compression/decompression means, connected to the input/output means of said optical disk drive sub- assembly, for compressing data transmitted into said sub-assembly, and for decompressing data transmitted from said sub-assembly; a process control means for controlling the compression/decompression means and the conversion means, so that one of a number of available emulations is performed by the controller, wherein the compression ratio may vary between the emulations.

15. The system as claimed in Claim 14, wherein, for each emulation in which compression is allowed, the compression/decompression means can operate in one of a number of available modes of operation, said modes including a bypass mode wherein the compression/decompression means is bypassed.

16. The system as claimed in Claim 14, further

_^ comprising a means for calculating the average compression ratio, and a display for displaying an average compression ratio during any writing operation to the optical disk. 17. The system as claimed in Claim 14, further comprising a means for calculating the average compression ratio, and a display for displaying, during read and decompression operations, the average compression ratio, said compression ratio being the compression ratio achieved during a prior writing of the data.

18. The system as claimed in Claim 14, wherein the conversion means includes means for converting from commands suitable for a random access, rewriteable disk to commands suitable for a sequential access, write once disk.

19. The system as claimed in Claim 18, wherein the random access commands are suitable for a Winchester hard drive.

20. The system as claimed in Claim 14, wherein the controller further comprises means for controlling setup parameters for communications compatibility with the host computer, and wherein the system further comprises a means for selecting the setup parameters.

21. The system as claimed in Claim 20, wherein the means for selecting the setup parameters includes a display viewable by a user, and manual controls accessible to a user. 22. The system as claimed in Claim 20, wherein the means for selecting the setup parameters includes a means for selecting one of a number of available preset configurations for the setup parameters.

23. The system as claimed in Claim 14, further comprising a first error detection means for detecting errors in communication between the computer and the compression/decompression circuit, and a second error detection means for detecting errors in communication between the compression/decompression circuit and the optical disk drive sub-assembly.

24. The system as claimed in Claim 23, further comprising an error correction means for detecting and correcting errors in reading from the optical disk.

25. The system as claimed in Claim 14, further comprising selection means for selecting one of said emulations.

26. The system as claimed in Claim 25, wherein the means for selecting one of the available emulations includes a terminal connected to the process control means. 27. The system as claimed in Claim 26, wherein the selection means comprises a display viewable by a user, and manual controls accessible to a user.

28. The system as claimed in Claim 27, further comprising a housing for enclosing the optical disk drive sub- assembly and the controller.

29. The system as claimed in Claim 28, wherein the housing has a size conforming to the full form factor standard of the computer industry.

30. The system as claimed in Claim 28, wherein the housing comprises a front panel, and the selection means are positioned thereon.

31. A method for writing digital data to an optical disk, comprising the steps:

(a), selecting a target compression ratio for digital data from a number of different available ratios; (b), compressing the digital data by at least the target compression ratio; and,

(c), writing the compressed data to an optical disk.

32. The method as claimed in Claim 31 , wherein the compression ratio lies in a range between 2:1 and 29:1. 33. The method as claimed in Claim 31 , further comprising a step (d), wherein information indicating that the stored data has been compressed is written to the optical disk.

34. The method as claimed in Claim 31 , further comprising a step (d), calculating the average compression ratio for the data and displaying said ratio.

35. A method for reading stored digital data from an optical disk, comprising the steps :

(a), reading data from the disk, said data indicating whether data within a block is compressed or not;

(b), reading the stored data from the disk; and, (c), decompressing the stored data, if the presence of compressed data was indicated in the step (a).

36. A method for preparing an optical disk drive system for writing digital data to, and reading digital data from, an optical disk, said digital data being provided by a host computer, said method comprising the steps:

(a) selecting the setup parameters for compatibility with the host computer; and,

(b) selecting an emulation for the optical disk, from a number of available emulations. 36. A method for preparing an optical disk drive system for writing digital data to, and reading digital data from, an optical disk, said digital data being provided by a host computer, said method comprising the steps:

(b) selecting an emulation for the optical disk, from a number of available emulations.

37. The method as claimed in Claim 36, wherein the step (a) includes selecting between a number of available preset configurations for the setup parameters.

38. The method as claimed in Claim 36, wherein in the step (a), selecting the setup parameters includes selecting the bus termination to be on or off.

39. The method as claimed in Claim 36, further comprising a step (c), applicable in writing to an optical disk, the step (c) including selecting a compression mode from a number of available compression modes.