AU2006200756B2 - A USB flash memory device for connecting to a USB-defined BUS - Google Patents

Description

I

-la- ARCHITECTURE FOR A UNIVERSAL SERIAL BUS-BASED PC FLASH DISK Field and Background of the Invention The present invention is related to semiconductor memory devices, and in particular to erasable and programmable non-volatile memory modules which are connected to a host platform using the USB PC Bus.

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

Erasable and programmable non-volatile memory modules, hereinafter referred to as flash memory or flash devices, are known in the art for storage of information. Flash devices include electrically erasable and programmable read-only memories (EEPROMs) made of flash-type, floating-gate transistors and are non-volatile memories similar in functionality and performance to EPROM memories, with an additional functionality that allows an in-circuit, programmable, operation to erase pages of the memory. One example of an implementation of such a flash device is given in U. S.

Patent No. 5,799,168, incorporated by reference as if fully set forth herein.

Flash devices have the advantage of being relatively inexpensive and requiring relatively little power as compared to traditional magnetic storage disks. However, in a flash device, it is not practical to rewrite a previously written area of the memory without a preceding page erase of the area. This limitation of flash devices causes them to be incompatible with typical existing operating system programs, since data cannot be written to an area of memory within the flash device in which data has previously been written, unless the area is first erased. A software management system, such as that disclosed in U. S. Patent No. 5,404,485, filed on March 5,1993, which is incorporated as if fully set forth herein, is required to manage these functions of the flash memory device.

Currently, these flash memory devices have a second limitation, which is that they must -2be either attached statically to the host platform, or attached and detached dynamically using the PCMCIA [Personal Computer Memory Card International Association] interface. Both implementations have drawbacks, including difficulty of use and high cost.

A more useful implementation would follow the USB standard, as described in the USB Specification Version 1.1 which is incorporated as if fully set forth herein. The USB standard offers a smaller form factor and greater ease of use for the end user, while lowering the cost of the implementation. This standard is specified to be an industrywide standard promoted by companies such as Compaq Computer Corporation, Microsoft, IBM and Intel to serve as an extension to the PC architecture with a focus on Computer Telephony Integration (CTI), the consumer, and productivity applications.

The criteria which were applied to define the architecture for the USB standard include the ease of PC (personal computer) peripheral expansion, low cost, support of transfer rates up to 12Mb/second and full support for real-time data, voice, audio, and compressed video. This standard also offers protocol flexibility for mixed-mode isochronous data transfers and asynchronous messaging, integration in commodity device technology and provision of a standard interface for rapid integration into any given host product. In addition, the USB standard represents a single model for cabling and attaching connectors, such that all of the details of the electrical functions, including bus terminations, are isolated from the end user. Through the standard, the peripheral devices are self-identifying, and support automatic mapping of functions to a driver.

Furthermore, the standard enables all peripheral devices to be dynamically attachable and re-configurable.

A system constructed according to the USB standard is described by three separate, defined areas: USB interconnection, USB devices and the USB host platform. The USB interconnection is the manner in which USB devices are connected to, and communicate with, the host platform. The associated functions and components include the bus topology, which is the connection model between USB devices and the host platform.

The USB physical interconnection has a tiered star topology. A hub is at the center of each star. Each wire segment is a point-to-point connection between the host platform and a hub or function, or a hub connected to another hub or function.

In terms of a capability stack, the USB tasks which are performed at each layer in the system include a data flow model and a schedule. A data flow model is the manner in which data moves in the system over the USB between data producers and data consumers. A schedule determines access to the interconnection, which is shared. Such scheduling enables isochronous data transfers to be supported and eliminates arbitration overhead.

The USB itself is a polled bus. The host controller on the host platform initiates all data transfers. All bus transactions involve the transmission of up to three packets. Each transaction begins when the host controller, on a scheduled basis, sends a USB packet describing the type and direction of transaction, the USB device address, and endpoint number. This packet is referred to as the "token packet." The USB device, to which the packet is addressed, selects itself by decoding the appropriate address fields. In a given transaction, data is transferred either from the host platform to a device or from a device to the host platform. The direction of data transfer is specified in the token packet. The source of the transaction then sends a data packet or indicates that the source has no data to transfer. The destination, in general, responds with a handshake packet indicating whether the transfer was successful.

The USB data transfer model between a source and destination on the host platform and an endpoint on a device is referred to as a "pipe". There are two types of pipes: stream and message. Stream data has no USB-defined structure, while message data does.

Additionally, pipes have associations of data bandwidth, transfer service type, and endpoint characteristics like directionality and buffer sizes. Most pipes come into existence when a USB device is configured. One message pipe, the default control pipe, always exists once a device is powered, in order to provide access to the configuration, status, and control information for the device.

The transaction schedule for the USB standard permits flow control for some stream pipes. At the hardware level, this prevents situations in which buffers experience underrun or overrun, by using a NAK handshake to throttle the data rate.

With the NAK handshake, a transaction is retried when bus time is available. The flow control mechanism permits the construction of flexible schedules which accommodate concurrent servicing of a heterogeneous mix of stream pipes. Thus, multiple stream pipes can be serviced at different intervals with packets of different sizes.

The USB standard, as described, has three main types of packets, including token packets, data packets and handshake packets. An example of each type of packet is shown in background art Figures 1-3. Background art Figure 4 shows an exemplary USB abstract device.

A token packet 10, as shown in background art Figure 1, features a PID (packet identification) field 12, specifying one of three packet types: IN, OUT, or SETUP. If PID field 12 specifies the IN packet type, the data transaction is defined from a function to the host platform. If PID field 12 specifies the OUT or SETUP packet type, the data transaction is defined from the host platform to a function.

An ADDR field 14 specifies the address, while an ENDP field 16 specifies the endpoint for token packet 10. For OUT and SETUP transactions, in which PID field 12 specifies that token packet 10 is an OUT packet type or a SETUP packet type, ADDR field 14 and ENDP field 16 uniquely identify the endpoint for receiving the subsequent data packet, shown in Figure 2, which follows after token packet 10. For IN transactions, in which PID field 12 specifies that token packet 10 is an IN packet type, ADDR field 14 and ENDP field 16 uniquely identify which endpoints transmit a data packet. A CRC5 field 18 contains the checksum, for determining that token packet 10 has been received without corruption. Only host platform can issue token packets 10, such that token packets 10 provide control over transmission of the subsequent data packets.

As shown in background art Figure 2, a background art USB data packet 20 also features a PID (packet identification) field 22 for identifying the type of data packet. Data packet also features a data field 24 for optionally containing data, and a CRC field 26 for containing the checksum as previously described.

Background art Figure 3 shows a background art USB handshake packet 28, which features only a PID (packet identification) field 30. Handshake packets 28 are used to report the status of a data transaction and can return values indicating successful reception of data, command acceptance or rejection, flow control, and halt conditions.

Only transaction types which support flow control can return handshake packets 28.

Handshake packets 28 are always returned in the handshake phase of a transaction and may be returned, instead of data packets 20, in the data phase of a transaction.

These three different types of packets are exchanged during various phases of the transaction which includes a USB device. A schematic block diagram of the functional blocks in a typical USB device 32 is shown in Figure 4 for an abstract background art USB device. USB device 32 typically includes a USB electrical interface 34, featuring a cable and a connector, which is a physical interface for receiving and transmitting electrical signals which are compatible with the USB specification as previously described. The signals are then passed to a logical interface 36, which includes one or more buffers, the device address decoder for decoding the address of the source device for the signals, and a SYNC field synchronizer for synchronizing the signals.

Information and structures required for management of USB abstract device 32 as a USB device are stored in a USB class control and enumeration engine 38. A function and device engine 40, also termed the "application", controls and manages the specific functions and properties of USB abstract device 32. In addition, function and device engine 40 also consumes and produces most of the data over the USB bus.

The USB specification does not define the relationship between different entities in USB abstract device 32, however. Rather, the USB specification describes only the requirements for the packets, and for the electrical and physical connection between USB abstract device 32 and the bus. Therefore the connections and relationships shown in background art Figure 4 are only one example of an implementation which fulfils the requirements of the USB specification. Thus, any specific device for fulfilling the USB specification must have a specifically defined and described architecture.

Unfortunately, no such architecture exists for a flash memory device containing one or more flash memory modules, which would enable the flash memory device to connect to a bus defined according to the USB specification and thereby to form part of a USB system on a host platform. For example, U. S. Patent No. 5,799,168 does not teach or suggest such an implementation for the flash device. As mentioned previously, such an architecture would be particularly useful for a number of reasons, including low cost, ease of use and transparency to the end user.

There is thus a need for, and it would be useful to have, an architecture for defining and describing a flash memory device which is compatible with a USB system and which follows the USB specification, such that the flash memory device could sit on a USBdefined bus and communicate with the host platform through this bus.

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

Summary of the Invention According to a first aspect, the invention provides a USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external data connector, comprising: at least one flash memory module; only a single external data connector, which connector is a USB connector adapted for connection to a USB-defined bus; a USB controller which interfaces with a host over said USB connector by a packet-based interface to said host and which at least one of reads and writes to said at least one flash memory module; and a housing enclosing said at least one flash memory module and said USB controller, which housing said single external USB connector crosses, wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said USB connector into actions for said at least one flash memory module.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive 00 sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

Ct 3 According to a second aspect, the invention provides a USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single IDintegral unit with a single external data connector, comprising: at least one flash memory module; S(b) only a single external data connector, which connector is a USB connector IDadapted for connection to a USB-defined bus; and a USB controller which interfaces with a host over said USB connector by a packet-based interface to said host and which at least one of reads and writes to said at least one flash memory module, wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said USB connector into actions for said at least one flash memory module.

According to a third aspect, the invention provides a USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external connector, comprising: at least one flash memory module; only a single external connector, which connector is a USB connector adapted for connection to a USB-defined bus; a USB controller which interfaces with a host over said USB connector by providing a block-device interface and which at least one of reads and writes to said at least one flash memory module; and a housing enclosing said at least one flash memory module and said USB controller, on which said single external USB connector is mounted, wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said USB connector into actions for said at least one flash memory module, and wherein said USB controller negotiates with said at least one flash memory module to determine at least one feature of the flash module geometry.

According to a fourth aspect, the invention provides a USB flash memory device for connecting to a USB-defined bus, the flash memory device, comprising: at least one flash memory module adapted for storing data and contained in said device; a USB connector adapted for connection to a USB-defined bus; and a USB controller operative to communicate via said connector with a host and which provides a read/write hard disk block device interface to said host for accessing said at least one flash memory module, wherein said controller comprises a command interpreter which interprets read and write block commands received as command packets including an op-code followed by arguments and encapsulated within USB application packets over said USB connector into actions for said at least one flash memory module; and wherein said memory device is dynamically attachable/detachable from said USBdefined bus.

According to a fifth aspect, the invention provides a method of using a flash memory device, comprising: providing a unitary flash memory device with an external computer data connector, which connector is a USB connector; attaching said device as a plug and play device to a USB port on a host system; and accessing said flash memory as a hard disk from said host, via said USB port, wherein said device is operable to provide only a packet-based interface.

According to a sixth aspect, the invention provides a method of using flash memory storage on a USB connection, comprising: providing a flash memory storage module; attaching said module to a USB connector on a host; and accessing at least 64 Mbit of data stored on said module, wherein said attaching comprises attaching as a plug and play block-device and wherein said accessing comprises receiving read/write block commands as packets encapsulated inside USB packets with an opcode followed by one or more parameters -9and wherein said accessing comprises translating by said module, a logical address of a block-device command into a physical address of said module.

According to a seventh aspect, the invention provides a USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external connector, comprising: at least one flash memory module; only a single external connector, which connector is a USB connector adapted for connection to a USB-defined bus; a USB controller which interfaces with a host over said USB connector by providing a block-device interface and which at least one of reads and writes to said at least one flash memory module; and a housing enclosing said at least one flash memory module and said USB controller, on which said single external USB connector is mounted, wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said USB connector into actions for said at least one flash memory module, wherein said USB controller negotiates with said at least one flash memory module to determine at least one feature of the flash module geometry, and wherein said at least one feature comprises a bus width.

According to an eighth aspect, the invention provides a USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external connector, comprising: at least one flash memory module; only a single external connector, which connector is a USB connector adapted for connection to a USB-defined bus; a USB controller which interfaces with a host over said USB connector by providing a block-device interface and which at least one of reads and writes to said at least one flash memory module; and a housing enclosing said at least one flash memory module and said USB controller, on which said single external USB connector is mounted, wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said USB connector into actions for said at least one flash memory module, wherein said USB controller negotiates with said at least one flash memory module to determine at least one feature of the flash module geometry, and wherein said at least one feature comprises an interleaving.

According to a ninth aspect, the invention provides A USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external connector, comprising: at least one flash memory module; only a single external connector, which connector is a USB connector adapted for connection to a USB-defined bus; a USB controller which interfaces with a host over said USB connector by providing a block-device interface and which at least one of reads and writes to said at least one flash memory module; and a housing enclosing said at least one flash memory module and said USB controller, on which said single external USB connector is mounted, wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said USB connector into actions for said at least one flash memory module, and wherein said controller is configured to emulate a block device in a manner compatible with a standard operating system.

According to a tenth aspect, the invention provides a USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external connector, comprising: at least one flash memory module; only a single external digital data connector, which connector is a connector adapted for connection to a USB-defined bus; a USB controller which interfaces with a host over said connector by providing a block-device interface and which at least one of reads and writes to said at least one flash memory module; and -11a cable coupled to said connector at one end thereof and including a standard peripheral USB connector on another end thereof, wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said connector into actions for said at least one flash memory module.

Another aspect of the invention provides a method of communicating between a host platform and a USB compliant flash memory device, comprising: transmitting a write packet from said host to said device; performing said write; transmitting a status packet from said device to said host; extracting an address of said write from said status packet by said host; and said host associating said address with said write command.

Hereinafter, the term "computer" includes, but is not limited to, personal computers (PC) TM

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having an operating system such as DOS, WindowsTM, OS/2 T M or Linux; Macintosh

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computers; computers having JAVATM-OS as the operating system; and graphical workstations such as the computers of SunMicrosystems and Silicon Graphies, and other computers having some version of the UNIX operating system such as AIX TM or SOLARISTM of SunMicrosystemsTM; or any other known and available operating system, including operating systems such as Windows CE

T

M for embedded systems, including cellular telephones, handheld computational devices and palmtop computational devices, and any other computational device which can be connected to a network. Hereinafter, the term "Windows

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includes but is not limited to TMTM*

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Windows95

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Windows 3.x T M in which is an integer such as WindowsNT T M Windows98 T M Windows CETM and any upgraded versions of these operating systems by Microsoft Inc. (Seattle, Washington, USA).

Brief Description of the Drawings A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: -12- FIG. 1 is a schematic block diagram of a background art USB token packet structure; FIG. 2 is a schematic block diagram of a background art USB data packet structure; FIG. 3 is a schematic block diagram of a background art USB handshake data packet structure; FIG. 4 is a schematic block diagram of an exemplary background art USB device; FIG. 5 is a schematic block diagram of a system with a flash USB device functionality according to the present invention; FIG. 6 is a schematic block diagram of the USB Flash disk; FIG. 7 is a schematic block diagram of a flash identification request packet; FIG. 8 is a schematic block diagram of a flash identification status packet; FIG. 9 is a schematic block diagram of a flash write request packet; FIG. 10 is a schematic block diagram of a flash write status packet; FIG. 11 is a schematic block diagram of a flash read request packet; FIG. 12 is a schematic block diagram of a flash read status packet; FIG. 13 is a schematic block diagram of a flash erase request packet; and FIG. 14 is a schematic block diagram of a flash erase status packet.

Detailed Description of the Invention The present invention is of a flash memory device, containing one or more flash modules, in which the flash memory is mapped to the address space of an ASIC or a controller which has a USB-defined electrical interface and a USB-defined logical interface. This controller/ASIC (hereinafter termed a "controller") supports the USB functionality according to the USB standard, thereby supporting enumeration onto the USB bus, as well as data reception and transmission over USB pipes to and from USB endpoints. This controller also supports the functionality and control of the flash memory device, as well as the processing of command and data packets from the host controller. The host controller uses one of several possible protocols, either standard or proprietary, to signal the next command to be performed to the USB flash controller.

Thus, the entire device acts as a dynamically attachable/detachable non-volatile storage device for the host platform.

While the invention is susceptible to various modifications and can be implemented using many alternative forms, the embodiment is shown by way of example in the -13drawings and will be described in details in the following pages. It should be understood that one of ordinary skill in the art appreciates that the present invention could be implemented in various other ways. The intention is to cover all modifications and alternatives falling within the spirit of the current invention.

The principles and operation of a USB flash device and system according to the present invention may be better understood with reference to the drawings and the accompanying description, it being understood that these drawings are given for illustrative purposes only and are not meant to be limiting.

Referring now to the drawings, Figure 5 is a schematic block diagram of the main components of a flash memory device and system according to the present invention. A flash memory system 42 includes a host platform 44 as shown. Host platform 44 operates USB flash device 46 as a non-volatile storage space.

Host platform 44 is connected to USB flash device 46 according to the present invention through a USB cable 48. Host platform 44 connects to USB cable 48 through a USB host connector 50, while USB flash device 46 connects to USB cable 48 through a USB flash device connector 52. Host platform 44 features a USB host controller 54 for controlling and managing all USB transfers on the USB bus.

USB flash device 46 features a USB flash device controller 56 for controlling the other components of USB flash device 46 and for providing an interface for USB flash device 46 to the USB bus, USB flash device connector 52 and at least one flash memory module 58. Flash memory module 58 is preferably an array of flash memory modules 58 in which the data is stored.

Whenever USB flash device 46 becomes connected to host platform 44, a standard USB enumeration process takes place. In this process host platform 44 configures USB flash device 46 and the mode of communication with USB flash device 46. Although there are many different methods for configuring USB flash device 46, for the purposes of clarity only and without intending to be limiting, the present invention is explained in greater detail below with regard to a method in which host platform 44 issues commands and -14requests to USB flash device 46 through one endpoint. Host platform 44 queries USB flash device 46 through the other endpoint for status changes, and receives related packets if any such packets are waiting to be received.

Host platform 44 requests services from USB flash device 46 by sending request packets to USB host controller 54. USB host controller 54 transmits packets on USB cable 48.

These requests are received by USB flash device controller 56 when USB flash device 46 is the device on the endpoint of the request. USB flash device controller 56 then performs various operations such as reading, writing or erasing data from or to flash memory module(s) 58, or supporting basic USB functionality such as device enumeration and configuration. USB flash device controller 56 controls flash memory module(s) 58 by using a control line 60 to control the power of flash memory module(s) 58, and also through various other signals such as chip enable, and read and write signals for example. Flash memory module(s) 58 are also connected to USB flash device controller 56 by an address/data bus 62. Address/data bus 62 transfers commands for performing read, write or erase commands on flash memory module 58, as well as the addresses and data for these commands as defined by the manufacturer of flash memory module(s) 58.

In order for USB flash device 46 to notify host platform 44 on the result and status for different operations requested by host platform 44, USB flash device 46 transmits status packets using the "status end point". According to this procedure, host platform 44 checks (polls) for status packets and USB flash device 46 returns either an empty packet if no packets for new status messages are present, or alternatively returns the status packet itself.

A more detailed structure of the functional components of USB flash device 46 is shown in Figure 6. USB flash device 46 includes the physical and electrical interface defined for the USB standard, shown here as USB flash device connector 52 and a connector interface 64. USB flash device connector 52 receives the electrical signals from USB cable 48 which carries electrical signals from host controller (not shown). These signals are then passed through connector interface 64. Every millisecond, a USB frame is carried on the USB-defined bus, such that packets could be sent to USB flash device 46.

Connector interface 64 then receives these packets through a first interface component, which is a combined physical and logical interface 66. A functional interface 68 is specifically designed to receive token packets as defined in the USB specification and as previously described with regard to Figure 1. These token packets are related only to particular functional aspects of USB flash device 46 which are required for the USB standard, and do not have any relation to particular application of USB flash device 46 as a flash disk according to the present invention. These token packets and their respective returned data packets enable USB host controller 54 (not shown) and host platform 44 (not shown) to identify USB flash device 46 and allocate resources for USB flash device 46 on the USB bus. Thus, functional interface 68 only supports USB functionality needed for the identification and registration of USB flash device 46 on the USB bus.

USB flash device 46 also features an application packet extractor 70 which extracts the application data and commands from the USB application packets, such that application packet extractor 70 supports only application related packets. Next, any requests to USB flash device 46 by host platform 44 (not shown), in the form of read, write, identify and erase commands, are interpreted by an application command interpreter 72. For any commands which involve data or an address, such as read, write and erase commands, an address resolve module 74 translates the address from the logical address space to the physical address space. Host platform 44 (not shown) relates to a linear address space of logical addresses, while USB flash device 46 contains at least one, and preferably a plurality of, flash modules 58, each of which has a physical address space. Thus, a translation must be performed between the logical address space of host platform 44 (not shown) and physical address space or spaces of USB flash device 46. There are many ways to implement such a translation which are suitable for the present invention. One example of a suitable implementation of an address translation method is described with regard to U. S. Patent No. 5,404,485, previously incorporated by reference as if fully set forth herein, which teaches a method for managing a flash memory as a flash disk and which is suitable for operation with the present invention.

A data handler 76 handles data related aspects of any received commands, and -16conveying the data through functional interface 68 to and from flash module(s) 58.

Optionally and preferably, data handler 76 performs any error correction and detection methods. Application command interpreter 72, data handler 76 and address resolve module 74 all operate with an underlying Memory Technology Driver (MTD) 78 to write, read or erase a particular flash module 58 and the desired address on that flash module 58.

Host platform 44 checks for status changes in USB flash device 46 and reads status packets from USB flash device 46 when a new status packet is available. Using these status packets, USB flash device 46 can transmit, to host platform 44, the results of different commands issued by host platform 44 in its requests (not shown). For example, the read command status packet contains one of the available status words such as "success", "error" or "invalid address", which enables host platform 44 to determine the result of the read command (not shown). Similarly, the erase status packet contains a status word indicating the completion of the erase process. A write status packet is used by USB flash device 46 to notify host platform 44 about the result of the write command, for example whether the command was successful or erroneous, and whether USB flash device 46 is ready for additional write requests from host platform 44.

A Memory Technology Driver, or MTD 78 typically contains routines to read, write and erase the flash memory device controlled by the controller operating MTD 78. In addition, MTD 78 optionally contains an identification routine for recognizing the proper type of flash memory device for which MTD 78 was designed, so that the controller can determine which MTD should be activated upon interacting with a particular flash memory device array. In addition, an identification routine should be able to detect the size of the array of flash memory devices, including the number of flash memory devices within the array, and various features of the flash array geometry, such as interleaving and bus width. This information later enables host platform 44 platform to determine the address space and size of the storage media. U. S. Patent No.

5,799,168, previously incorporated by reference, discloses an example of such an MTD for a flash device.

Using the above described protocol and architecture, host platform 44 can optionally -17implement any application which is implementable with any regular memory mapped or I/O mapped flash memory device. For example, host platform 44 can give a standard block device interface to each application, such as a magnetic storage medium "hard disk" drive, as disclosed in the previously described U. S. Patent No. 5,404,485.

As an example of a preferred embodiment of the present invention, the operation of a host system connected to a USB flash device according to the present invention is described with regard to the processes of identifying, programming, reading and erasing the flash device. For the purposes of illustration only and without intending to be limiting in any way, the exemplary USB flash device has an array of two flash memory modules, each of which is 64Mbit in size. The address translation table is within the flash device so that host platform operates with logical addresses. All commands and return codes between the flash device and the host platform are carried on USB data packets, and are transferred through USB data pipes. The exact structure of the packets, pipes and timings are described in the USB specification.

The operation of the exemplary device and system according to the present invention is as follows. When the USB flash device is first connected to the host platform, the USB host controller assigns an address to the USB flash device on the USB bus, and also assigns resources as described in the USB specification. The USB flash device actually asks the host platform to assign these resources, and must inform the host platform how much of these resources are needed. Thus, the USB flash disk can optionally support slower device speeds if the USB host platform has already allocated resources to other devices.

The USB controller also negotiates with the flash modules and determines the size and manufacturing type of these modules. The controller then builds an identification structure holding this information, as well as the translation table and logical address space.

After the USB host controller identifies the USB flash device, the host platform often uploads a USB client driver. The driver issues an identification request command to the USB host controller, causing the controller to transmit an identification data packet shown in Figure 7. Identification packet 80 contains PID field 22 and checksum field 26, 18as described previously for background art Figure 2. Identification packet 80 also contains an "identify" operation code in an operation code field 82. The packet extractor of the USB flash device receives identification data packet 80 and transfers the operating code of the "identify" command to the application command interpreter.

In response to the "identify" command, the flash device then sends an identification data packet 84, shown in Figure 8. In addition to the fields shown in Figure 7, identification data packet 84 also contains information about the size of the flash device in a flash device size field 86, as well as information about the size of the minimal erase unit for erasing the flash memory in an erase unit size field 88.

All of the packets described in this example are only data packets which are sent on the USB bus. Before each data packet is sent, a USB token packet is transmitted, instructing the USB controller as to the identity of the device end point to which the data packet should be transmitted. Upon successful reception of the packet, the USB controller issues a USB ACK packet as described in the USB specification.

Once the device drivers in the host platform receive this status packet, the drivers can start issuing read and write commands to the USB flash device with the application commands. When a write request is sent, a USB data packet with the operation code for the "write" command, and the buffer containing the data, is transferred to the USB flash device. A write data packet 90 is shown in Figure 9, which again includes the fields shown previously in Figure 8, except that write data packet 90 also includes a write field 92 with the "write" operational code; an ADDR field 94 with the logical address to be written; a LEN field 96 with the length to be written; and a DATA field 98 which contains the actual data to write. The packet extractor extracts the operational code from write data packet 90 and transfers this code to the application command interpreter. The logical address is transferred to the address resolve module which translates this logical address to a physical address on one of the flash modules. The data handler optionally calculates error correction and detection mechanisms if employed by the USB flash device. Once all of the flash memory modules are ready, a "write" command is sent to the flash module or modules containing the physical address, which may optionally span across more than one flash module to the MTD block. The MTD block then issues a "write" command on the data/address bus which connects the flash modules to the USB device controller. Once the operation is complete and a status packet is returned to the -19- MTD, the result of the operation is transmitted to the host controller and passed to the device driver in the host platform.

When the flash controller finishes the writing process, the controller signals to the host platform that the status of the USB flash memory device has changed, by sending a "write status" packet 100, as shown in Figure 10. In place of data field 98, write status packet 100 contains a status field 102. The host platform reads the status packets from the flash memory device, and from write status packet 100, the host platform retrieves information on the completion status of the write command by reading status field 102.

In this example, the flash memory device repeats ADDR field 94 and LEN field 96 in order for the host platform to have a reference to the specific command related to status packet 100.

As shown in Figure 11, a "read request" packet 104 contains the operation code for the "read" command in a read field 106, and the logical address of the desired location from which the flash controller should read in an ADDR field 108. Upon receiving this command, the flash controller issues a read command to the MTD block, after the address resolve module has translated the address contained in ADDR field 108 to a specific physical address in one of the flash components.

When the flash controller receives the data from the flash device, either after the read command was issued, or if an error occurred, the flash controller sends a signal to the host platform to indicate that a new status packet must be read. The host platform issues a read request and receives a "read status" packet 110 as shown in Figure 12. Read status packet 110 contains the address of the read data in ADDR field 108, as well as the length of the read data in a LEN field 112 and the data itself in a data field 114. Read status packet 110 also features the status word, according to which the operation was completed, in a status field 116. The read operation can be completed with many different status situations such as success, fail, error detected, invalid address, invalid length and so forth.

When the host platform needs to erase an erase unit in the flash device, the host platform issues an "erase request" packet 118, shown in Figure 13. This packet contains the 20 "erase" operation code in an erase field 120, and the logical address of the erase unit in an ADDR field 122. Upon receiving such a request, the flash controller translates the logical address to a physical erase unit address on one of the physical address spaces of the flash modules, and issues an erase command to the MTD block.

The erase process generally takes more time then a read or write process. When this erase process is finished, the controller notifies the host platform a new status packet is ready to transmit. The controller then transmits an "erase status" packet 124, as shown in Figure 14. Erase status packet 124 contains the address of the erased unit in ADDR field 122, thereby providing the host platform with a reference to the erase requests. The status according to which the operation was completed is provided in a status field 126.

It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the spirit and the scope of the present invention.

Claims (49)

1. A USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external data connector, comprising: ID(a) at least one flash memory module; only a single external data connector, which connector is a USB connector Sadapted for connection to an USB-defined bus; IND a USB controller which interfaces with a host over said USB connector by a packet-based interface to said host and which at least one of reads and writes to said at least one flash memory module; and a housing enclosing said at least one flash memory module and said USB controller, which housing said single external USB connector crosses, wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said USB connector into actions for said at least one flash memory module.

2. A device according to claim 1, wherein said block commands are encapsulated as packets within USB application packets.

3. A device according to claim 1, wherein said block commands are provided as an op- code followed by parameters.

4. A USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external data connector, comprising: at least one flash memory module; only a single external data connector, which connector is a USB connector adapted for connection to a USB-defined bus; and a USB controller which interfaces with a host over said USB connector by a packet-based interface to said host and which at least one of reads and writes to said at least one flash memory module, 00 -22- wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said USB connector into Sactions for said at least one flash memory module.

5. A USB flash memory device according to any one of the preceding claims, wherein IND said controller both reads and writes to said at least one flash memory module. S6. A USB flash memory device according to any one of the preceding claims, wherein IND said USB controller provides a standard block device interface to said host for accessing ,I 10 said at least one flash memory module.

7. A USB flash memory device according to any one of claims 1-5, wherein said USB controller provides a hard disk interface to said host for accessing said at least one flash memory module.

8. A USB flash memory device according to any one of the preceding claims, wherein said device is operative to support a plug and play connection with said host.

9. A USB flash memory device according to any one of the preceding claims, wherein said device acts as a dynamically attachable/detachable non-volatile storage device for said host. A USB flash memory device according to any one of the preceding claims, wherein said USB controller is implemented as a single integrated circuit separate from said flash memory, which is operative to communicate via said connector with a host and which provides an interface to said host for accessing said at least one flash memory module.

11. A USB flash memory device according to claim 10, wherein said single integrated circuit comprises an ASIC (application specific integrated circuit).

12. A USB flash memory device according to any one of the preceding claims, wherein said USB controller comprises: a USB interface which supports a USB protocol; and 00 -23- O (ii) a functionally separate flash memory interface which at least one of treads and writes to said at least one flash memory module.

13. A USB flash memory device according to any one of claims 1-11, wherein said controller comprises: INO a USB-defined electrical interface; (ii) a USB-defined logical interface; O (iii) a packet extractor adapted to extract an operational code from a ION write data packet; S 10 (iv) an address resolver adapted to translate a logical address from a write packet into a physical address on one or more of said at least one flash memory module.

14. A USB flash memory device according to any one of the preceding claims, wherein said device provides logical to physical address translation between said host and said at least one flash memory module. A USB flash memory device according to any one of the preceding claims, wherein said USB controller interprets write commands after extracting data to be written from said packets.

16. A USB flash memory device according to any one of the preceding claims, wherein said USB-bus is connected to said host and wherein said host provides commands to said USB controller using a proprietary protocol.

17. A USB flash memory device according to any one of claims 1-15, wherein said USB-bus is connected to said host and wherein said host provides commands to said USB controller using a standard protocol.

18. A USB flash memory device according to any one of the preceding claims, comprising an address/data bus interconnecting said USB controller and said at least one flash memory module. 00 -24- O 19. A USB flash memory device according to any one of the preceding claims, wherein said USB controller negotiates with said at least one flash memory module to determine Sits size and manufacturing type and uses said determined at least one of size and type to Sgenerate at least one of a translation table and address space. IN 20. A USB flash memory device according to claim 19, wherein said USB controller negotiates to determine size. ID21. A USB flash memory device according to claim 19, wherein said USB controller negotiates to determine manufacturing type.

22. A USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external connector, comprising: at least one flash memory module; only a single external connector, which connector is a USB connector adapted for connection to a USB-defined bus; a USB controller which interfaces with a host over said USB connector by providing a block-device interface and which at least one of reads and writes to said at least one flash memory module; and a housing enclosing said at least one flash memory module and said USB controller, on which said single external USB connector is mounted, wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said USB connector into actions for said at least one flash memory module, and wherein said USB controller negotiates with said at least one flash memory module to determine at least one feature of the flash module geometry.

23. A USB flash memory device according to claim 22, wherein said at least one feature comprises a size.

24. A USB flash memory device according to claim 22, wherein said at least one feature comprises a bus width. 00 A USB flash memory device according to claim 22, wherein said at least one feature comprises an interleaving.

26. A USB flash memory device according to any one of the preceding claims, wherein IND said controller includes a plurality of chip enable signal lines for attaching to a plurality of flash memory modules. IND 27. A USB flash memory device according to any one of the preceding claims, wherein said controller is adapted to work with a plurality of different types of flash memory modules.

28. A USB flash memory device according to any one of the preceding claims, wherein said controller uses at least two USB endpoints for communication with a host system.

29. A USB flash memory device according to any one of the preceding claims, wherein said connector is directly attached to said controller by a combined physical/logical interface.

30. A USB flash memory device according to any one of claims 1-28, wherein said connector is directly attached to said controller.

31. A USB flash memory device according to any one of the preceding claims, wherein said at least one flash memory module comprises a plurality of flash memory modules.

32. A USB flash memory device for connecting to a USB-defined bus, the flash memory device, comprising: at least one flash memory module adapted for storing data and contained in said device; a USB connector adapted for connection to a USB-defined bus; and a USB controller operative to communicate via said connector with a host and which provides a read/write hard disk block device interface to said host for accessing said at least one flash memory module, 00 -26- O wherein said controller comprises a command interpreter which interprets read and write block commands received as command packets including an op-code followed by Sarguments and encapsulated within USB application packets over said USB connector into actions for said at least one flash memory module; and wherein said memory device is dynamically attachable/detachable from said USB- INO defined bus. S33. A USB flash memory device according to claim 32, wherein said device comprises ION a plurality of flash memory modules.

34. A USB flash memory device according to any one of the preceding claims, wherein said flash memory module comprises at least 64Mbit. A USB flash memory device according to any one of the preceding claims, wherein said flash memory module is organized as a plurality of blocks, each block including a plurality of individually addressable sectors, each of said sectors corresponding to a file system sector and wherein said memory allows erasing only in units of said block.

36. A USB flash memory device according to any one of the preceding claims, wherein said device uses a software management system to manage said flash memory as a flash disk.

37. A USB flash memory device according to any one of the preceding claims, wherein said flash memory device comprises a USB flash disk.

38. A USB flash memory device according to any one of the preceding claims, wherein said flash memory module is contained in said device.

39. A device according to any one of the preceding claims, wherein a single said application packet includes an entire read command and its parameters. A device according to any one of the preceding claims, wherein a single said application packet includes a write command and its parameters. 00 -27- S41. A device according to claim 40, wherein said application packet includes data to be written for said write command. Ct

42. A device according to any one of the preceding claims, wherein said interface sends a command before sending parameters for the command. INO

43. A USB flash memory device according to any one of the preceding claims, wherein said USB controller negotiates with said at least one flash memory module to determine ISO its type and uses said determined type to determine an MTD (Memory Technology Driver) to use for said flash memory.

44. A device according to claim 43, wherein said controller notifies said host that it is ready after said negotiation.

45. A method of using a flash memory device, said method comprising: providing a unitary flash memory device with an external computer data connector, which connector is a USB connector; attaching said device as a plug and play device to a USB port on a host system; and accessing said flash memory as a hard disk from said host, via said USB port, wherein said device is operable to provide only a packet-based interface.

46. A method according to claim 45, wherein said external connector comprises an integral connector.

47. A method according to any one of claims 45-46, wherein said device comprises only a single external connector.

48. A method according to any one of claims 45-47, wherein said device consists substantially of said connector, a controller and said flash memory.

49. A method according to any one of claims 45-48, wherein said device comprises a single controller which provides both USB functionality and flash memory functionality. 00 -28- oO A method according to any one of claims 45-49, wherein said device comprises at Sleast twice 64 Mbit flash memory storage capacity.

51. A method according to any one of claims 45-50, comprising performing address INO translation from a hard disk address space to a flash memory address space on said V) rdevice. ID52. A method of using flash memory storage on a USB connection, said method 1o comprising: providing a flash memory storage module; attaching said module to a USB connector on a host; and accessing at least 64 Mbit of data stored on said module, wherein said attaching comprises attaching as a plug and play block-device and wherein said accessing comprises receiving read/write block commands as packets encapsulated inside USB packets with an opcode followed by one or more parameters and wherein said accessing comprises translating by said module, a logical address of a block-device command into a physical address of said module.

53. A method according to claim 52, wherein said flash memory module is comprised in a unitary flash memory storage device.

54. A method according to claim 52, wherein said flash memory module acts as a flash disk. A method according to any one of claims 52-54, wherein said module comprises a single external data connector.

56. A USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external connector, comprising: at least one flash memory module; 00 -29- 0 only a single external connector, which connector is a USB connector adapted for connection to a USB-defined bus; S(c) a USB controller which interfaces with a host over said USB connector by providing a block-device interface and which at least one of reads and writes to said at least one flash memory module; and ID(d) a housing enclosing said at least one flash memory module and said USB controller, on which said single external USB connector is mounted, 0 wherein said controller comprises a command interpreter which interprets read and write IDblock commands received as application packets over said USB connector into actions S 10 for said at least one flash memory module, wherein said USB controller negotiates with said at least one flash memory module to determine at least one feature of the flash module geometry, and wherein said at least one feature comprises a bus width.

57. A USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external connector, comprising: at least one flash memory module; only a single external connector, which connector is a USB connector adapted for connection to a USB-defined bus; a USB controller which interfaces with a host over said USB connector by providing a block-device interface and which at least one of reads and writes to said at least one flash memory module; and a housing enclosing said at least one flash memory module and said USB controller, on which said single external USB connector is mounted, wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said USB connector into actions for said at least one flash memory module, wherein said USB controller negotiates with said at least one flash memory module to determine at least one feature of the flash module geometry, and wherein said at least one feature comprises an interleaving. 0-30- 0O O 58. A USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external connector, Scomprising: at least one flash memory module; only a single external connector, which connector is a USB connector adapted IDfor connection to a USB-defined bus; a USB controller which interfaces with a host over said USB connector by providing a block-device interface and which at least one of reads and writes to said at IDleast one flash memory module; and a housing enclosing said at least one flash memory module and said USB controller, on which said single external USB connector is mounted, wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said USB connector into actions for said at least one flash memory module, and wherein said controller is configured to emulate a block device in a manner compatible with a standard operating system.

59. A system comprising a device according to claim 58 and a host including a standard operating system installed thereon. A USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external connector, comprising: at least one flash memory module; only a single external digital data connector, which connector is a connector adapted for connection to a USB-defined bus; a USB controller which interfaces with a host over said connector by providing a block-device interface and which at least one of reads and writes to said at least one flash memory module; and a cable coupled to said connector at one end thereof and including a standard peripheral USB connector on another end thereof, 00 -31- O wherein said controller comprises a command interpreter which interprets read and write block commands received as application packets over said connector into actions Sfor said at least one flash memory module.

61. A device according to claim 60, wherein said connector is a USB connector. IN

62. A device according to any one of claims 60-61, wherein said device is operative to act as a flash disk to said host.

63. A method of communicating between a host platform and a USB compliant flash memory device, said method comprising: transmitting a write packet from said host to said device; performing said write; transmitting a status packet from said device to said host; extracting an address of said write from said status packet by said host; and said host associating said address with said write command.

64. A USB flash memory device for connecting to a USB-defined bus, the flash memory device being provided as a single integral unit with a single external data connector, said device being substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. A USB flash memory device for connecting to a USB-defined bus, the flash memory device being substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples.

66. A method of using a flash memory device, said method substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. 00 -32- S^ 67. A method of using flash memory storage on a USB connection, said method substantially as herein described with reference to any one of the embodiments of the Sinvention illustrated in the accompanying drawings and/or examples.

68. A method of communicating between a host platform and a USB compliant flash IND memory device, said method substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or Sexamples.