Flash Memory Card Basics

By: The Editor
Adding memory to your mobile device is one of the best ways to ehance your mobile experience. Many PDA's have only enough memory to store and run a few main programs. Adding memory will allow you to overcome this limitation and make it possible to store lots of software, images and music on your device.

Chances are that if you own a pocket pc, digital camera, computer, or new video game console, you have had experience with so-called flash memory cards. These small devices can hold a relatively large amount of data for their size. Because they are so small they have been the ideal removeable storage device of small digital products like digital cameras. Although they have existed in the market place for over 5 years now, they come in greater variety and larger storage capacities than ever before.

Flash memory is used in a variety of ways with a many different types of electronic devices. You can find flash memory as SmartMedia (used in digital cameras), Memory Sticks (also used in digital cameras), PCMCIA Type I and II memory cards (used in laptops), CompactFlash (yes, also used in digital cameras), and nearly all computer BIOS chips. (continued...)

How does Flash Memory Work?

Flash memory chips uses basically the same memory technology found in your hard drive, or ROM. The flash chip is an example of a EEPROM chip, which means that it is made up of a complex grid of columns and rows with two transistors at each grid intersection. One of the two transistors is called a floating gate, and receives 10 to 13 volts of electricity from the column known as the bitline. The charge in the floating gate forces excited electrons through with a negative charge. A cell sensor then detects the level of charge going through the floating gate in a given interval. If the flow through the gate is has greater than 50% of the charge, then it is given the value of 1. When the current falls below 50% then a 0 is designated. The sequence of 1's and 0's is essentially stored into sections along the chip known as blocks, and your data is stored.

Flash Cards for Digital Cameras

Flash cards are most commonly used in digital cameras. If you are looking for the right type of flash card for your digital camera, you must keep in mind that only CompactFlash (CF), SmartMedia (SM), Memory Stick (MS), MultiMediaCard (MMC), Secure Digital (SD), and xD-Picture Cards (xD) are compatible.

CompactFlash Cards -These cards contain both memory chips and a controller. Most digital cameras that utilize CompactFlash cards can use any storage size CF card up to around .5 - 1GB with no major issues. CF cards with a storage of 2GB or more, however, use the FAT-32 file system, and some cameras may not be able to read this kind of memory. There are two styles of CompactFlash cards - Type I (3.3mm thick) and Type II (5mm thick) CF cards. Digital cameras with Type I slots can't use Type II cards. However, cameras with Type II slots can use both.

SmartMedia - These memory cards are typically smaller than a lot of the CompactFlash cards. They save space by providing a storage system essentially integrated onto a plastic card, much like a credit card device. Card sizes are usually around 64mb - 128mb, with some older cameras not capable of handling this high capacity.

Memory Stick - This flash memory devised was first devised by Sony in 1999. It is still used exclusively with their Cyber-shot digital cameras and many of their Handycam video camcorders. The typicaly storage size of the memory stick is 128mb.

To learn which flash memory type is best for your PDA or other digital device, read your device manual or visit the manufacturer website.


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