Abstract:
A portable memory device is provided that is capable of easy connection to a personal computer via a universal serial bus (USB) port, IEEE 1394 (i.e., firewire) or similar port. Included in the portable memory device is a compression/decompression engine capable of compressing and decompressing data. Data residing on a personal computer or other host platform is compressed by the engine and saved to the memory of the portable memory device. Compressed data is retrieved and decompressed by the engine and transmitted to the personal computer for use by the user. Embodiments of the present invention thus provide a highly convenient system and apparatus for users to access and save larger quantities of data to a relatively small device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a continuation of U.S. patent application Ser. No. 10/147,124 filed May 16, 2002, issued as U.S. Pat. No. 7,082,483 on Jul. 25, 2006, which claims priority to International Application No. PCT/SG02/00086 filed May 13, 2002; the contents of which are incorporated herewith by reference in their entirety.  
         [0002]     This application also is related to the following U.S. patent applications, each of which is owned by the assignee of the present invention and is incorporated by reference in its entirety herein:  
         [0003]     U.S. patent application Ser. No. 09/803,173, entitled “PORTABLE DATA STORAGE DEVICE CAPABLE OF BEING DIRECTLY CONNECTED VIA USB PLUG TO A COMPUTER”; U.S. patent application Ser. No. 09/803,157, entitled “PORTABLE DATA STORAGE DEVICE HAVING SECURE MODE OF OPERATION”, issued on Apr. 12, 2005 as U.S. Pat. No. 6,880,054; U.S. patent application Ser. No. 09/898,365, entitled “A PORTABLE DEVICE HAVING BIOMETRICS-BASED AUTHENTICATION CAPABILITIES”; and U.S. patent application Ser. No. 09/898,310, entitled “A PORTABLE DEVICE HAVING IOMETRICS-BASED AUTHENTICATION CAPABILITIES”. 
     
    
     BACKGROUND OF THE INVENTION  
       [0004]     1. Field of the Invention  
         [0005]     The present invention relates to the field of storage of electronic data. More particularly, the present invention relates to the compression and decompression of data stored to a portable memory device.  
         [0006]     2. Background of the Invention  
         [0007]     Portable memory devices, sometimes referred to as “key chain” memory devices or Thumbdrives™ (which is a trademark of the assignee of the present invention), are small portable data storage devices. These devices have become a class of indispensable computer peripherals that are widely utilized in business, educational and home computing. These devices are very small in comparison with other data storage devices such as personal computers (PCs), personal digital assistants (PDAs), magnetic disks, or compact disks (CDs). Indeed, the name “keychain” memory device describes the devices as similar in size to a key. Portable memory devices are generally not permanently fitted to a particular host platform, such as a PC. Rather, they can be conveniently attached to and removed from any computer having the appropriate connection port (e.g., a serial bus port like a USB port, or IEEE 1394 port (“Firewire”)). Thus, these portable data storage devices enable a user to transfer data among different computers that are not otherwise connected. Because these devices utilize a non-volatile solid-state memory (e.g., flash memory) as the storage medium, they do not require moving parts or a mechanical drive mechanism for accessing data. The absence of a drive mechanism enables portable data storage devices to be more compact than surface storage devices such as magnetic disks and CDs. Also, because there are no moving parts, reading and writing to the memory can be done much more rapidly than to magnetic disks and CDs. Portable data storage devices also have a much higher memory capacity than magnetic disks, holding up to 256 megabytes, as compared to 1.4 megabytes for magnetic disks.  
         [0008]     Although storing data to a portable memory device has proven useful, the utility of these devices is limited by their inability to store larger quantities of data without increasing their size.  
       SUMMARY OF THE INVENTION  
       [0009]     Accordingly, it is an object of the present invention to provide a system and apparatus that enables users to save larger quantities of data to a portable memory device than the current state of the art would allow. This would allow manufacturers to increase the amount of data that can be stored to the memory of these devices without increasing the physical size of the memory and thus the size of the devices. Additionally, this would have the added benefit of allowing manufacturers to decrease the size of these devices without decreasing the amount of data that such devices are capable of storing.  
         [0010]     These and other objects are achieved by the present invention comprising a portable memory device that is capable of easy connection to a host platform such as a PC via a USB port, IEEE 1394 (i.e., firewire) or similar port. Included in the device is flash memory, read-only-memory (ROM), random-access-memory (RAM), USB controller, and a micro controller. In addition, a data compression and decompression engine is included in the portable memory device to compress/decompress data as it is stored and retrieved from memory.  
         [0011]     The portable memory device (Thumbdrive™) is connected to a host platform such as a personal computer (PC) by a USB connector inserted into the PC&#39;s USB port. Data to be saved to the portable memory device is transmitted by the PC in the form of data packets to a working buffer in the portable memory device. The compression engine retrieves the data from the buffer and compresses each packet of data. Compressed data packets are stored in the flash memory. To retrieve data, the compression/decompression engine retrieves the data from the flash memory and decompresses it. The decompression engine places the decompressed data in the working buffer where it is then transferred to the host platform.  
         [0012]     Typically, the compression/decompression software is located in the ROM then loaded into micro controller for execution. In an alternative embodiment, the compression/decompression engine resides in an ASIC chip in the portable device.  
         [0013]     The compression/decompression features of the portable device are invisible to the user. The user saves data but is not aware that it is being compressed. In an alternative embodiment, the user is aware of these features and enables/disables the compression feature as desired. Disabling the compression feature has the effect of increasing the speed at which the data can be saved. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The objects, features, and advantages of the present invention will be apparent from the following detailed description of the preferred embodiment of the invention with references to the following drawings.  
         [0015]      FIG. 1  is a block diagram illustrating functional blocks of one embodiment of the portable memory device according to the present invention and an illustrative configuration thereof.  
         [0016]      FIG. 2 . illustrates a flow diagram that describes how the host platform communicates commands to the portable memory device.  
         [0017]      FIG. 3 . illustrates a flow diagram that describes how data is transmitted, compressed and saved to the memory of the portable memory device.  
         [0018]      FIG. 4 . illustrates a flow diagram that describes how compressed data saved to the memory of a portable memory device is accessed. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     The present invention will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather these embodiments are provided so that this disclosure is thorough and complete and fully conveys the invention to those skilled in the art. Indeed, the invention is intended to cover alternatives, modifications and equivalents of these embodiments, which are included within the scope and spirit of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it is clear to those of ordinary skill in the art that the present invention may be practiced without such specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present invention.  
         [0020]      FIG. 1  is a block diagram illustrating functional blocks of one embodiment of the portable memory device and system of the present invention and an illustrative configuration thereof.  FIG. 1  shows a portable memory device  100  (a small handheld device capable of fitting substantially in a closed fist) that is connected via a universal serial bus (USB) port IEEE 1394 (i.e., firewire) or similar port connector  40  to a USB port (or similar port)  192  of the host platform  195  (such as a personal computer). In the preferred embodiment, the connection is made without wire or cable interconnection. Host platform  195  is coupled to a power supply circuit  150  located in portable device  100 . Power supply circuit  150  draws power from host platform  195  and serves as a power source for various components of portable device  100 .  
         [0021]     Referring still to  FIG. 1 , the portable memory device  100  includes a micro controller  160 , flash memory  180 , and a data compression/decompression engine  190 . It is understood that micro controller  160  could also be a general purpose microprocessor.  
         [0022]     In one embodiment, a working buffer  165  is located in the micro controller. In an alternative embodiment, the working buffer  165  is located outside of the micro controller  165  (e.g., in the RAM  110 ). In the preferred embodiment, the working buffer has 16 kilobytes of capacity.  
         [0023]     It should be appreciated that data compression/decompression engine  190  maybe implemented in various ways within the scope of the present invention. In one embodiment, compression/decompression engine  190  is implemented as firmware stored in a non-volatile memory  110  within portable device  100 . In another embodiment, data compression/decompression engine  190  is implemented as part of micro controller  160 . In still another embodiment, compression/decompression engine  190  is implemented as a processor separate from micro controller  160 . In other words, within the scope of the present invention, compression/decompression engine  190  is not required to reside in a particular location in the portable device  100 . Instead, where compression/decompression engine  190  is to be placed is a design choice, thus affording design flexibility to suit different applications in which the present invention can be utilized.  
         [0024]     Data compression/decompression engine  190  compresses data after the data is transferred from the host platform  195  to the portable memory device  100 . The data is transferred in the form of data packets passed along a USB bus. The data compression/decompression engine  190  retrieves the data from the working buffer  165  (typically one sector at a time) and compresses the data. In the preferred embodiment, the data is compressed to 50% of its original size. Thus a packet of 512 bytes of data will be compressed to 256 bytes. After compression, the data is stored to the flash memory  180 . The compression/decompression engine  190  also decompresses data stored to the flash memory  180  and transfers the data to the host platform  195 .  
         [0025]     In this embodiment, the portable device includes a USB device controller  130 , which serves to control the communication between portable device  100  and host platform  195 , such as a USB-compatible PC having a USB host controller  197  therein.  
         [0026]     With reference still to  FIG. 1 , portable device  100  also includes a volatile memory  120  and a non-volatile memory  110 . In a preferred embodiment, volatile memory  120  is a random access memory (RAM) that serves as a working memory for micro controller  160  during its operation. Non-volatile memory  110  is a read-only memory (ROM) in this embodiment and can be used to store firmware that performs various functions of portable memory device  100 .  
         [0027]     Additionally, in this embodiment, portable device  100  includes a write-protect switch  170  which, when activated, triggers micro controller  160  to disable write-access to flash memory  180 . It should be appreciated that write-protect switch  170 , like compression/decompression engine  190 , may be implemented in various ways within the scope of the present invention. For example, write-protect switch  170  can be implemented by software (e.g., firmware stored in a non-volatile memory), as part of micro controller  160 , or as a processor unit separate from micro controller  160 . In an alternative embodiment, the write-protect switch  170  can be a manual switch which is manually operated by the user.  
         [0028]     In a currently preferred embodiment as illustrated in  FIG. 1 , microprocessor  160  controls various components of portable device  100 , including USB device controller  130 , ROM  110 , and RAM  120  (and execution of firmware code stored therein).  
         [0029]     Optionally, portable device  100  further includes a USB port (not shown) that is provided as a convenient feature that can be used to couple other USB-compatible device(s) to the portable device  100  via USB.  
         [0030]     In one embodiment, driver software (not shown), application programming interface (API) (not shown) and monitoring software (not shown) reside in the host platform  195  and communicate with USB host controller  197  to facilitate the operation of portable device  100 .  
         [0031]     The architecture of a portable data storage device is described in U.S. patent application entitled “A Portable Device Having Biometrics-Based Authentication Capabilities” with Ser. No. 09/898,365, filed on Jul. 3, 2001 and in U.S. patent application entitled “Portable Data Storage Device Capable of Being Directly Connected Via USB Plug to a Computer” with Ser. No. 09/803,173.  
         [0032]      FIG. 2  illustrates a flow diagram of the operation that occurs when the user connects the portable device  100  to the host platform  195  (step  205 ) and initiates the saving of data to the portable device  100 . In step  205 , upon being coupled to a host platform  195 , portable device  100  undergoes an initialization procedure. In a currently preferred embodiment, the initialization procedure involves establishing communication with the host platform  195  and ensuring the host platform  195  is aware that portable device  100  has been coupled thereto. Host platform  195  requests services from portable device  100  by sending request packets to USB host controller  197 . USB host controller  197  transmits packets through USB port  192  to USB connector  140 . Portable device  100  then performs various operations such as reading, writing or erasing coupled with compressing and decompressing data from or to flash memory  180 .  
         [0033]     In step  210 , host platform  195  may send a request to portable memory device  100  to write data to flash memory  180  in the form of a write command. In step  215 , USB controller  130  receives write command. Write command typically indicates the number of packets of data to follow that are to be saved.  
         [0034]      FIG. 3  illustrates a flow diagram of the operation that occurs when data is transferred to the portable device to be compressed and written to the flash memory  180 . Host platform  195  transmits a first data packet to USB controller  130  (step  303 ). In one embodiment, in accordance with the USB 2.0 standard, each data packet is the equivalent of one sector of memory or 512 bytes. In an alternative embodiment, in accordance with USB standard 1.1, each data packet is 64 bytes.  
         [0035]     USB Controller  130  receives packet of data from host platform  195  (step  305 ). USB controller  130  transmits data packet to working buffer  165  (step  310 ). In the preferred embodiment, working buffer  165  can hold a maximum of 16 kilobytes of data. If working buffer  165  reaches maximum capacity and can no longer store additional data, then the next data packet may be rejected and a negative acknowledgement (NAK) communication is sent by micro controller  160  to host controller  195  indicating that the rejected data packet was not received (steps  312  and  313 ). Host controller  195  then retransmits rejected data packet (step  303 ). This process of packet rejection and retransmission continues until the working buffer  165  has capacity to accept an additional data packet (step  314 ).  
         [0036]     Micro controller  160  executes data compression/decompression engine  190  (Step  315 ). Compression/decompression engine  190  operates on packets of data stored in working buffer  165  (Step  320 ) in a First In/First Out scheme whereby data packets are compressed in the order that they are stored to working buffer  165  with the first packet stored in working buffer  165  being the first to be compressed and transferred to flash memory  180 . In the preferred embodiment, data is compressed to 50% of its original size. In the preferred embodiment, when operating on a USB 2.0 standard, compression engine  190  operates to compress one sector (512 bytes) of data at a time. In an alternative embodiment, when operating on the USB 1.1 standard, compression engine  190  operates to compress 64 bytes of data at a time. Compressed data is saved to flash memory  180  (Step  325 ).  
         [0037]     Memory mapping is controlled by the micro controller  160 . In the preferred embodiment, the host platform (and user) are unaware that the data is being compressed. To the host platform, data appears to fill sectors in the flash memory  180  as if the data were not compressed (i.e., 512 bytes of non-compressed data per sector). Thus compressed data written to the first sector would appear to the host controller to fill one entire sector. In reality, the data is compressed from 512 to 256 bytes and is saved to half the sector space that would be needed for the data had it not been compressed. Thus the second packet of data, after it is compressed from 512 bytes to 256 bytes, may also be saved to the first sector. To the host controller, the second data packet, which in reality is saved to the first sector, will appear to be saved to the second sector. Similarly, the first data packet saved to second sector will appear to be saved to the third sector and the second data packet saved to the second sector will appear to be saved to the fourth sector.  
         [0038]     Typically standard 2 bit error detection and 1 bit correction mechanisms are employed.  
         [0039]     If there is another packet of data, then host controller  195  transmits the packet of data to USB controller  130  (step  335  and  303 ). Data compression engine  190  continues to compress additional packets of data stored to working buffer  165  (step  320 ). When there are no more data packets to be compressed, then the data compression and storage session ends.  
         [0040]      FIG. 4  illustrates the steps by which data is retrieved from the memory  180  of the portable memory device  100  and decompressed.  
         [0041]     In step  410 , user connects the portable device  100  to a host platform  195 . In step  410 , upon being coupled to a host platform  195 , portable device  100  may undergo the initialization procedure described previously. Host platform  195  requests services from portable device  100  by sending request packets to USB host controller  197 . USB host controller  197  transmits packets through USB port  192  to USB connector  140 .  
         [0042]     Host platform  195  may send a request to portable device  100  to read data requested by user (step  420 ) in the form of a read command. USB controller  130  receives the read command (step  425 ). Read command indicates the location of the data in the flash memory  180  and number of packets of data to be read. Because host platform  195  is unaware that data is compressed, the read command will request data that is not necessarily in the sector in which the host platform  195  believes it to be. For example, as discussed previously, the second data packet, which in reality is saved to the second half of the first sector, will appear to the host controller  195  be saved to the second sector. Similarly, the first data packet saved to second sector will appear to be saved to the third sector and the second data packet saved to the second sector will appear to be saved to the fourth sector. Thus, host platform&#39;s  195  data request may indicate that a particular packet of data is stored to the second sector, where in reality, it is stored to the second half of the first sector. To account for this, micro controller  160  operates to retrieve requested data from flash memory  180  in accordance with the manner in which it was saved (step  325 ).  
         [0043]     In step  430 , micro controller  160  executes data compression/decompression engine  190 . Compression/decompression engine  190  retrieves packets of requested data from flash memory  180  (step  445 ). Compression/decompression engine  190  acts to decompress dates (step  447 ). Decompressed data is transferred to working buffer  165  (step  450 ). Decompressed data is transferred to USB controller  130  (step  455 ). In step  460 , data packet is transferred to the memory (e.g., RAM) of the host platform  195 .  
         [0044]     Data compression/decompression engine  190  continues to retrieve and decompress data from flash memory  180  until all data requested has been decompressed and transferred to host platform  195 .  
         [0045]     Alternatively, host platform  195  may send a request to portable device  100  to read directory of data stored to flash memory  180 . User can then view directory on host platform  195  to determine which data user wishes to retrieve from flash memory  180 .  
         [0046]     It is to be understood that the above description is only of the preferred embodiments of the invention. One skilled in the art may devise numerous other arrangements without departing from the spirit and scope of the invention. The invention is thus limited only as defined in the accompanying claims.