The Universal Serial Bus (USB) is a specification to establish communication between devices and a host controller. Originally designed for personal computers, the USB is intended to replace many varieties of serial and parallel ports. For example, USB connects many computer peripherals such as mice, keyboards, digital cameras, printers, personal media players, flash drives, external hard drives, and the like. Although designed for personal computers, USB has found application in a broad variety of other data communication contexts.
The USB has evolved through three major revisions, and several minor ones. The USB 1.0 specification, introduced in 1996, supported a data transfer rate of 1.5 Mbit/s, now referred to as “low speed.” USB 1.1 introduced a “full speed” data transfer rate of 12 Mbit/s. USB 2.0, introduced in 2001, features a “hi-speed” rate of 480 Mbit/s. The USB 3.0 specification was released in late 2008, with controller chips available in early 2009. USB 3.0 defines a SuperSpeed data rate of 4.8 Gbit/s.
Flash memory is a non-volatile, solid state, digital data storage medium. Technically a type of EEPROM, NAND type flash (the most commercially common form of flash memory) is not usually byte-programmable, but must be read, written, and erased on a block basis. Additionally, wear leveling (dynamically remapping the physical memory to evenly spread physical write/erase cycle stress), bad block mapping, and other functions unique to NAND flash memory often require a dedicated controller for mass storage devices utilizing NAND flash as a storage medium.
The MultiMedia Card (MMC) is a flash memory card standard that defines the physical dimensions and operational characteristics of a small, removable mass storage device employing NAND flash memory. Embedded MMC (eMMC) describes a memory architecture combining embedded NAND flash memory and a high-speed MMC controller in a standard package (e.g., integrated circuit). eMMC simplifies system design by freeing a system processor from low-level flash memory management tasks. SD/MMC (Secure Digital) is another standard for removable memory based on the MMC form factor, which also combines flash memory with a memory controller. The SD controller provides Digital Rights Management (DRM) support. e-MCC memory and SD/MMC card slots are commonly designed into consumer electronic devices, such as digital cameras and mobile phones, as a means of data storage and transfer.
Electronic devices deployed in the field, such as mobile cellular telephones, music players, digital cameras, satellite navigation receivers, and the like, are increasingly used to carry and render large quantities of digital content such as music, photographs and movies. The increasing data storage capacities of eMMC memory and SD/MMC cards reflect this fact. Due to the ever-increasing capacity of these cards, there is a need to accelerate data transfers between external sources and the storage memory. This need for speedy transfers from outside the electronic device is best met when the mobile platform's embedded system controller, or application processor, does not have to act as a mediator between a fast external host and the storage memory (e.g., eMMC memory and SD/MMC flash memory cards). Optimum speed is achieved when an accelerated storage controller is able to offload the fast transfer activity from the application processor. This concept is often known as side-loading. However, this capability conventionally means that the electronic device's application processor can no longer directly access its embedded or removable memory, and must instead request access to the stored data through the accelerated storage handler to which the memory is directly connected.
Conventional electronic devices do not have the ability to access storage memory via an intermediate device, due to traditional hardware and software architectures being designed for direct memory access. However, hardware architectures that can benefit from accelerated data and file transfers from an external host computer would be advantageous.
An Accelerated Storage Controller (ASC) in an electronic device allows both conventional (slower) application processor to memory interfaces to be employed transparently to existing software, while also allowing software configuration to realize an accelerated storage architecture on demand. Some use cases for the electronic device do not require accelerated storage, and a bypass mode does not require any modification to existing software. Other use cases (such as fast download of multiple gigabytes of media) benefit from an accelerated storage architecture offloading transfer from the electronic device application processor, but could also work with the traditional processor to memory interface, at the cost of slower downloads. Embodiments of the present invention provide for both these possibilities in a software-configurable architecture. Furthermore, a number of other connectivity options are provided under software control to optimize performance and connectivity for different use case scenarios.
One embodiment relates to an electronic device. This could be a portable device such as a mobile phone. The device includes a memory interface operative to provide mechanical and electrical connectivity to memory media. The device also includes a data communication bus connected to the memory interface, and an Application Processor Engine (APE) connected to the data communication bus. The APE is operative to execute application programs, and is further operative to write data to and read data from memory media connected to the memory interface via the data communication bus. The device further includes an Accelerated Storage Controller (ASC). The ASC includes a host port configurably connected to the data communication bus and a communication port operative to connect the ASC to an external host in data communication relationship. As used herein, the term “external host” does not, unless otherwise specified, imply a particular physical position relative to other elements comprised by ASC, but refers to the described feature of being operative to connect the ASC to an external host in data communication relationship. The ASC is configurably operative to transfer data between an external host and memory media connected to the memory interface, via the host port and the data communication bus. The ASC is further configurably operative to isolate the host port from the data communication bus to allow the APE to read and write memory media connected to the memory interface, via the data communication bus.
Another embodiment relates to a method of managing data transfers in an electronics device including an APE and ASC including a host port and a communication port, the APE and host port of the ASC both connected to a memory interface via a data communication bus. Data is transferred between the APE and memory media connected to the memory interface via the data communication bus. Data is also transferred between an external host connected to the communication port of the ASC and memory media connected to the memory interface via the host port of the ASC and the data communication bus.
The APE 12 is a processor which may comprise a microprocessor, microcontroller, Digital Signal Processor (DSP), programmable logic with appropriate firmware, a state machine, or the like. The APE 12 is operative to execute operating system and/or embedded application programs to provide functionality to the electronic device 10 (e.g., mobile cellular telephone, digital camera, or the like). The memory interface 14 may comprise an interface to embedded memory media, such as eMMC, or may comprise a memory card slot operative to accept, and connect to, removable memory media such as SD/MMC. The APE 12 conventionally writes data to memory media connected to the memory interface 14, and reads data from the memory media, via the data communication bus 16, as known in the art.
In one embodiment, the host port 22 and device port 20 implement USB host and USB device functionality, respectively. However, the present invention is not limited to such functionality. The device port 20 can be a “slave” port with respect to the data communication bus 16, and operative to accept and implement data transfer requests from the APE 12. For example, the APE 12 may write configuration data to the ASC 18, and/or may engage in handshaking or other protocol signaling with an external host via the USB interface 26, through the device port 20. Similarly, the host port 22 can be a “master” port with respect to the data communication bus 16, and operative to initiate and control data transfers to and from memory media connected to the memory interface 14. For example, an external host may transfer large amounts of data to and from the memory interface 14 via the host port 22 and communication port 26, without involving the APE 12.
In the embodiment depicted in
Several use cases, and their support and enablement by embodiments of the present invention, are discussed below. These specific use cases are explained to illuminate the advantages of the circuits and arrangements of embodiments of the present invention, and to provide an enabling disclosure. However, the present invention is not limited to any one, or even the sum of all, of the specifically delineated and described use cases discussed herein, but rather encompasses all embodiments and applications covered by the accompanying claims.
In implementing the use cases discussed below, either the APE 12 or the host port 22 of the ASC 18 (or both, in a time-multiplexed fashion) drive the control signals on the data communication bus 16 to perform bus transactions according to the data communication bus 16 protocol. That is, either the APE 12 or the host port 22 of the ASC 18 is an active master of the data communication bus 16. This can be implemented in numerous ways. In one embodiment, software configures the current bus master, such as by writing specific bits to control registers. In another embodiment, a bus arbitrator (not depicted in
One important use case is access by the APE 12 to the memory interface 14. This is straightforward in the embodiment depicted in
A second use case is access by the ASC 18 to the memory interface 14. For example, it may be required that an external entity (e.g., a PC having a USB 3.0 host interface) upload voluminous data, such as a movie, to embedded memory (e.g., eMMC) or a removable flash memory card (e.g., SD/MMC). Conventionally, the APE 12 would have to interface with the external host, accepting small amounts of data and writing them to the memory interface 14. According to one embodiment, the APE 12 is functionally disconnected from the data communication bus 16, and the host port 22 drives data transfers to/from the memory interface 14. The ASC 18 may accept data from an external host via the communication port 26, e.g., at USB 3.0 SuperSpeed data rates, and load the data directly into memory media connected to the memory interface 14. In one embodiment, buffer memory 24 facilitates such data transfer by decoupling the bus transactions on the data communication bus 16 (i.e., host port 22 to memory interface 14) from transactions received by the communication port 26. Of course, data may also be transferred from the memory interface 14 to an external host along the same path. In this use case, in the embodiment of
A method 100 of implementing, in the alternative, these two use cases by an electronic device 10, is depicted in
A third use case is access by the APE 12 to the ASC 18. For example, the APE 12 may configure the ASC 18 by writing control registers. As another example, the APE 12 may communicate with an external host via the communication port 26, such as by using USB 3.0 SuperSpeed data rates. Examples of cases in which the APE 12 of an electronic device implementing mobile cellular telephone functionality may need to communicate with software programs executing on an external PC include controlling Digital Rights Management (DRM) functions, calendar and address book synchronization, and providing cellular modem service to the PC. In this case, the APE 12 is the bus master; the device port 20 of the ASC 18 is the bus slave, and the host port 22 is functionally disconnected from the data communication bus 16. The memory interface 14 may for instance be logically disconnected from the bus, or in the case of an addressable bus, is simply not addressed for the APE 12 to ASC 18 transactions. In this use case, in the embodiment of
A fourth use case is “concurrent” access by the APE 12 to the ASC 18, and by the ASC 18 to the memory interface 14. The access is quasi-simultaneous—for example, implemented in a time-division multiplexing manner—since the data lines on the data communication bus 16 are shared. The quasi-simultaneous access may be implemented in a number of ways. For example, in one embodiment, configuration software simply alternately reconfigures the APE 12 and host port 22 to be active bus masters. In another embodiment, with a bus arbiter, the APE 12 and host port 22 may be given equal priority access, with the bus arbiter implementing a round-robin (or ping-pong) arbitration scheme. In yet another embodiment, access by the least-frequently using master may be interrupt driven. For example, the ASC 18 may transfer data to/from the memory interface 14, with the APE 12 providing, for example, DRM handshakes with the external host, or providing a USB enumeration response to the external host for some transfer classes. In this case, an access attempt by the APE 12 may cause the ASC 18 to provide an error response, and implement a “back off” of some predetermined duration, prior to initiating another data transfer on the data communication bus 16 to the memory interface 14.
According to embodiments of the present invention, an external high-speed device, such as a PC, maintains a high-speed access to high volume data storage memory on an electronic device, when the electronic device application processor does not natively support such high-speed data transfer. Embodiments of the present invention are applicable to a wide variety of electronic devices, including cellular telephones, digital cameras, portable media players, digital video cameras, satellite navigation receivers, and the like.
eMMC is provided in this description as an example of embedded memory media accessed via the memory interface 16. Similarly, SD/MMC is described herein as an example of removable memory media removably connected to the memory interface 16. However, the present invention is not limited to these specific industry standard products. For example, embedded memory media may comprise any digital storage media having a controller/interface that presents a standard memory interface 14 to master devices on the data communication bus 16, such as the APE 12 and the host controller 22. Similarly, removable memory media may comprise any removable non-volatile memory media, such as MMC, Reduced-Size MMC (RS-MMC), Dual-Voltage MMC (DV-MMC), MMCplus, MMCmobile, MMCmicro, SecureMMC, SD, SDIO, miniSD, microSD, CompactFlash, USB flash memory drives, Memory Stick, SD High Capacity (SDHC), SD Extended Capacity (SDXC), or the like, as well as any revisions or extensions of these standards.
USB is provided in this description as an example of a communication host 26 protocol. However, the present invention is not limited to the USB bus protocol, or any of its specific versions or revisions. In general, the communication host 26 of the ASC 18 may implement any serial or parallel data communication protocol known in the art, including RS-232, RS-488, any version or release of the USB standard, any optical protocol, a custom or proprietary protocol, or any other data communication protocol operative to exchange data between the ASC 18 and an external host.
The present invention may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
This application claims priority to U.S. Provisional Patent Application Ser. No. 61/290,151, titled “Memory Management System Supporting Both Direct and Managed Access to Local Storage Memory,” filed Dec. 24, 2009.
Number | Date | Country | |
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61290151 | Dec 2009 | US |