EE264v01| Application Note
Engineer-to-Engineer Note
EE-264
a
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Interfacing MultiMediaCardTM with ADSP-2126x SHARC Processors
Contributed by Aseem Vasudev Prabhugaonkar and Jagadeesh Rayala Rev 1 March 11, 2005
Introduction
This application note describes how to implement the interface between an ADSP2126x SHARC processor and a MultiMediaCardTM (MMC). The application note also describes the MMC command format and demonstrates with example code how an MMC card can be interfaced seamlessly with the SHARC processor's SPI port. Example code supplied with this application note implements the most commonly used commands of MultiMediaCard.
memory access voltage of 2.7 to 3.6 V, and a capacity from 4 MB to the gigabyte range.
About the ADSP-2126x SPI Port
The ADSP-2126x processor is equipped with a synchronous serial peripheral interface port that is compatible with the industry-standard Serial Peripheral Interface (SPI). The SPI port supports communication with a variety of peripheral devices including codecs, data converters, sample rate converters, S/PDIF or AES/EBU digital audio transmitters and receivers, LCDs, shift registers, micro-controllers, and FPGA devices with SPI emulation capabilities. Important features of ADSP-2126x SPI port include: Simple four-wire interface, consisting of two data pins, a device select pin, and a clock pin Full duplex operation, allowing simultaneous data transmission and reception on the same SPI port Data formats to accommodate little and big endian data, different word lengths, and packing modes Master and slave modes as well as multimaster mode in which the ADSP-2126x processor can be connected to up to four other SPI devices Open drain outputs to avoid data contention and to support multimaster scenarios
About MultiMediaCard
The MMC was introduced in 1998 and had an amazing reduction in cubic capacity compared with CompactFlashTM. MMC cards are now widely used in digital cameras, smart cell phones, PDAs, and portable MP3 players. Their intended use is to store information and content. The MMC consists of a 7-pin interface and supports two serial data transfer protocols viz. the MMC (MultiMediaCard) mode and SPI (Serial Peripheral Interface) mode. The maximum operating clock frequency used for serial communication in both modes can go up to 20 MHz. The data written in any of these modes can be read by host in either mode. The advantage of MMC supporting SPI mode is that MMC can be interfaced seamlessly to many controllers or DSP processors, which have onchip support for SPI. Most MMCs have a communication voltage from 2.0 to 3.6 V, a
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