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Secure Digital memory (known as SD or SD Card) is a type of memory card created by Matsushita Electronic, SanDisk and Toshiba in January 2000. Secure Digital memory is a memory specifically developed to meet new safety requirements in the field of electronic audio and video devices. It therefore includes a copyright protection system that satisfies the SDMI (Secure Digital Music Initiative) standard.
The architecture of the SD cards is based on NAND-type flash memory circuits (EEPROM).
The Secure Digital memory has small dimensions (24.0mm x 32.0mm x 2.1mm), equivalent to those of a postage stamp, and weighs barely 2 grammes.
Data are accessed using a 9-pin lateral connector achieving a transfer speed of 2 Mb/s with the potential to go up to 10 MB/s.
SD memory access time is around 25µs for first access and cycles of 50 ns for subsequent cycles.
