The SD card contains four types:
- SDSC: Standard capacity Card, sd1.1/1.0 specification, capacity 1MB-2GB, file format FAT32
- SDHC: High capacity SD card, SD2.0 specification, capacity 4g-32g, file format is FAT32
- SDXC: Capacity-enlarged secure memory card, capacity 32G-2TB, file format extFAT32
- SDIO: A peripheral interface is defined on the SD standard. An important difference between the SDIO and SD card specifications is the addition of low-speed standards. The Sdio card requires only SPI and 1-bit SD transfer mode.
SD card Detection A total of three ways:
- When booting the command by CMD to detect the presence of the T card, this method does not support hot-swappable
- The signal tcard_detect is connected to the interrupt controller by means of the T-mount. The tcard_detect signal is low when no card is inserted. After inserting the T card, the signal tcard_detect is pulled high to a high level, resulting in an interrupt. That is, hot-swapping is achieved. Note: From low to high or from high to low trigger, is the hardware and software collaboration, can be set
- Through the CD/DAT3 signal to detect, the CD/DAT3 signal is connected to the interrupt controller, and through the 470K resistor pull down, in the absence of T card insertion, the signal is low, one but a T card insertion, the T card internal through 50Kohm to pull the DATA3 signal high to high level, resulting in an interrupt, Hot swapping is achieved.
SD Card Related Knowledge summary
