By PURPLELEC | 30 October 2023 | 0 Comments
Embedded storage-SD card
With the application of embedded systems in the field of industrial control, large-capacity data storage is a problem that needs to be solved. Common embedded storage solutions include Flash memory chips, SD cards and USB flash drives. Comprehensive comparison, SD card is a good choice. SD cards have the characteristics of large storage capacity (more than 128GB), easy portability and support for SPI communication.
The full name of SD card is "Secure Digital Memory Card", which is translated into Chinese as "Secure Digital Memory Card". S It is a memory card based on semiconductor flash memory technology. It is widely used in portable devices (such as digital cameras, mobile phones, PAD, etc.). It is also widely used in the field of industrial control embedded storage.
The SD card was first jointly developed by Japan's Panasonic, Toshiba and the American company SanDisk in 1999. It is about the same size as a postage stamp, weighs only about two grams, but has an amazing storage capacity.
SD cards are divided into ordinary SD cards and micro SD cards (Micro SD, also called TF card) in appearance. Micro SD cards (TF cards) are smaller in size and do not have a write-protect switch. Through the card adapter, the micro SD card can be converted into an ordinary SD card for use.
SD card supports two communication modes: SD mode and SPI mode. The default is SD mode, which can achieve high-speed reading and writing. Generally, microcontrollers are used to operate in SPI mode. The method to enter SPI mode is to set the chip select signal (CS) to low level when the SD card receives the reset command (CMD0). However, before sending the reset command, pulse data greater than 74 clocks must be sent in order to increase the supply voltage inside the SD card and synchronize the clock. The SD card has 9 pins, and their definitions are different in SD mode and SPI mode.
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