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Understanding secure digital I/O performance in systems and cards
2004-05-12 Article Rating:  / 0
One of the more recent mobile device expansion standards is Secure Digital I/O (SDIO), an evolutionary offshoot of Secure Digital Memory (SD/MMC) technology. This 24-page whitepaper by Seung Yi, Chief Technologist at Codetelligence Inc., explores some of the performance issues that must be considered when designing systems incorporating SDIO.
From the introduction . . . The proliferation of feature-rich mobile devices, with ever-increasing processing capabilities has created a desire for expansion options previously seen only in the laptop/desktop space. Consumers are increasingly demanding expansion options to increase capacity (storage) or capabilities (features) in order to fend off, for the moment, the threat of obsolescence and future (largely unknown) needs. Multimedia content has been the driving force in the industry to create the necessary standards and technology in audio players, digital cameras, personal digital assistants and smart phones. Expansion began with memory storage in the form of memory cards (with a plethora of existing standards) utilizing low cost NAND flash technology. As mobile devices become increasingly more powerful the line between a single function consumer electronic device and a more general computing device becomes blurred. One indication of this trend has been in the standardization of I/O expansion in mobile devices. Previously I/O expansion in mobile devices consisted of proprietary hardware/software interfaces, typically only available to the specific manufacturer and in many cases to a specific device model. Soon afterwards a generation of devices adapted technology from the realm of laptop computing in the form of CompactFlash I/O. CompactFlash I/O expansion offered a relatively painless way to incorporate PCMCIA standards to a more mobile-friendly form factor. Demand for thinner and lighter devices has pushed the need for even smaller I/O expansion technologies. Enter Secure Digital I/O (SDIO), introduced in the later part of 2001, as an evolutionary offshoot of Secure Digital Memory technology. SDIO is based on similar electronics and mechanicals borrowed from the original SD memory card specification, and offers device manufacturers a convenient way to support memory and I/O cards in the same slot. SDIO extends the specification to meet I/O specific requirements in terms of power, plug and play, and I/O commands and signals. The addition of I/O expansion capability to an SD memory slot can be implemented at minimal incremental cost, largely due to the availability of more capable controllers. This paper describes some of the performance issues that should be taken into consideration when designing SDIO capable systems and cards. Design issues can be encountered on both host and card side implementations, from silicon to software. This paper provides a general overview of SD Memory and SDIO and then goes on to describe some application specific and common issues encountered in the design of such systems. The information presented here is based on experience in system software design for various SDIO capable platforms including software architecture, silicon-specific host drivers and card-specific control software. (504 KB PDF file download) The above text and the full downloadable whitepaper are copyright © 2004 Codetelligence Inc. All rights reserved. Reproduced by WindowsForDevices.com with permission. Related stories:
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