SD cards

The Secure Digital (SD) cards are a non-volatile memory card created by manufacturers like Toshiba, SanDisk and Matsushita. These cards are used for portable devices in cameras, handheld computers, camcorders, PDSs, mobile phones, media players, video game consoles and GPS receivers. These SD cards have capacities that range from 1MB to even 4GB. SDHC cards overlap that capacity beginning at 4GB and going up to 32GB. SDXC (meaning eXtended Capacity), is a type of card still in developing and will reach capacities of up to 2TB.

The SD cards are a very popular format. All the SD cards have the same physical shape as the SDHC cards and this can sometimes cause confusion among the clients. The SD cards rely on the old MultiMediaCard (MMC) format, but there are many differences.

A SD card is asymmetrically shaped so that it will not be inserted placed upside down. The MMC cards enter in any position they are placed but they do not work if they are inverted. Many SD cards are thicker than MMCs. A SD card has the following measures: 32 mm × 24 mm × 2.1 mm. The MMCs are as thin as 1.4 mm and they do not have the write-protect switch. These “thin SDs” are described but only in theory because they can rarely be seen on the market. They are replaced by miniSDs or microSDs.

The electrical contacts are placed beneath the card’s surface and protects them from contact. SD cards have a transfer rate between 10-20 MB/s but recently the MMC standards have improved as well.

The devices that use SD slots use thinner MMCs and standard SDs do not fit the thin MMC slots. With SD slots you can also use miniSD cards. The SD cards can also be accessed using a floppy disk drive and a FlashPath adapter.