MMC card briefing

MMC card briefing 1. MMC card registersCID 128bit mandatory RCA 16bit mandatory DSR 16bit optional CSD 128bit mandatory OCR 32bit mandatory 2. Register descriptionOCR-operation conditions register stores the VDD voltage profile of the card, read only CID-card identification register carries the card ID, used during the card identification procedure CSD-card-specific data register provides the information on how to access the card contents, e.g. 1) Data Format 2) error correction type 3) maximum data access time 4) data transfer speed 5) whether DSR register is available RCS-relative card address register carries the card address assigned by the host during the card identification DSR-driver stage register, optional used to improve the bus performance for extended operating conditions E. g Bus length, transfer rate or number of cards 3. MMC BusCMD-bidirectional operation OD/PP mode dat-bidirectional operation in PP mode CLK-Unidirectional operation in PP mode VDD-Power Supply vss1, vss2-od: Open-drainpp: push-pull 4. MMC bus circuitry dimo- ROD: used to switch between OD and PP modes rdat and RCMD: Used to prevent DAT and CMD from being flushed when no card is inserted or when all cards are in the high-impedance status 5. SPI ModeThe SPI mode contains an optional communication protocol provided by a flash-based mmccard, it is mainly defined for situations where the system does not have a dedicated MMC host controller and does not have high communication speed requirements. SPI defines only one physical connection Standard for MMC communication, with only one subset of the MMC protocol and command. The advantage of SPI is that the existing SPI interface can be either hardware or software, saving the need to design a dedicated hardware MMC host controller. The disadvantage of SPI is that compared with the MMC protocol, the data transmission rate is very low, and the number of cards that can be supported is relatively small (usually only one card), and each card needs to be selected by one chip, unlike the MMC protocol, you can select a card through the RCA. SPI signal: CS-chip CLK-clock dataIn-host-> card data dataout-host <-card data SPI data transmission is performed by an integer multiple of the bytes, byte-alignedspi is always performed based on CS signals. Only single/multiple block read/write operations are supported, and sequential operations are not supported. 6. SPI vs MMC pinout MMC SPI1. CLR CS2. cmd di3. vss1 vss4. VDD vdd5. CLK sclk6. vss2 vss27 dat do 7. Registers in SPI ModeIn spi mode, only some bits of the three registers can be accessed. These bits are: Cid 16bit CSD 16bit OCR 32bit. 8. File Systems for MMC Card 8.1 Hard Disk-like File System w/Partition TableThe first data block is used to store Partition Table 8.2 Dos fat file system w/o Partition Table   8.3 Universal File System for MMC Card