SD卡操作时序说明.doc

How to Use MMC/SDC Update: November 3, 2010 The Secure Digital Memory Card (SDC below) is the de facto standard memory card for mobile equipments. The SDC was developped as upper-compatible to Multi Media Card (MMC below). SDC compleant equipments can also use MMCs in most case. There are also reduced size versions, such as RS-MMC, miniSD and microSD, with the same function. The MMC/SDC has a microcontroller in it. The flash memory controls (erasing, reading, writing, error controls and wearleveling) are completed inside of the memory card. The data is transferred between the memory card and the host controller as data blocks in unit of 512 bytes, so that it can be seen like a generic hard disk drives from view point of upper level layers. The currentry defined file system for the memory card is FAT12/16 with FDISK patitioning rule. The FAT32 is defined for only high capacity (= 4G) cards. This page describes the basic knowledge and miscellaneous things that I become aware, on using MMC/SDC with small embedded system. I believe that this information must be a useful getting started notes for the people who is going to use MMC/SDC on the electronics handiwork projects. Pinout miniSD | microSD Right photo shows the contact surface of the SDC/MMC. The MMC has seven contact pads and the SDC has nine contact pads that two additional contacts to MMC. The three of the contacts are assigned for power supply so that the number of effective signals are four (MMC) and six (SDC). Therfore the data transfer between the host and the card is done via a synchronous serial interface. The working supply voltage range is indicated in the operation conditions register (OCR) and it should be read and comfirmed the operating voltage range. However, the supply voltage can be fixed to 3.0/3.3 volts because the all MMC/SDC work at supply voltage of 2.7 to 3.6 volts at least. The current consumption on write operation can reach up to some ten miliamperes, so that the host system should co