Number 320 - January 2010

Digital Memory Cards
by Jason Mills,
Digital cameras are designed to capture images via an electronic image sensor. They utilize a form of removable storage called flash memory, one of the essential digital camera accessories. Flash memory is a non-volatile (no power consumption) EEPROM (Electronic Erasable Programmable Read-Only Memory) type that can be re-used and re-programmed. It offers fast access time for reading information and images.    A flash memory stores information in a number of memory cells, made from floating-gate transistors. It is made with a card case durable enough to withstand pressure, temperature and water. It can be inserted into a camera compartment. Images are taken and processed automatically. It has a range capacity of 128 megabytes to a number of gigabytes. More pictures can be stored in a high capacity memory.    Below are a few examples of flash memories. CompactFlash    CompactFlash is a 50-pin digital camera memory card. It is used in many applications to interface with PCs, PDAs and printers. Type I and Type II, are the 2 physical sizes available. Some cameras accept only Type I. Type II is much thicker and has a higher capacity. One common Type II card is the MicroDrive memory card. It also has a built-in controller chip. This allows higher transfer rates on cameras with larger internal buffers.    CompactFlash was built something similar to Intel's NOR-based flash memory. It became the oldest and most inexpensive format in the market today. It is available in 512 MB (megabytes) to 100 GB (gigabytes) capacity. 1 GB abd 16 GB are two of the popular choices in North America and Europe.	CF memory cards are the most desirable types because of its rugged design. It withstands more physical damage as compared to other portable storage devices. It lacks the write protection switch that other devices have in common. Secure Digital (SD)    Secure Digital is one of the non-volatile memory card formats widely used in digital cameras, computers and mobile phones. The slim and compact design is just about the size of a postage stamp. A decoder software of SD enables you to play music and video clips.    SD cards are supported by the older MultiMediaCard (MMC). They have a transfer rate of 10-2- Mbytes. They support at least three of the transfer modes. These include the One-bit SD mode (separate data channels, cammands and transfer format), Four-bit SD mode (use reassigned and extra pins) and the SPU mode (subset of the SD protocol use with microcontrollers). Memory Stick    A memory stick is a kind of digital data storage lauched by Sony in October 1998. It is designed for small digital products because of its compact design. The 8 MB memory stick is available in4, 8, 16, 32, 64, and 128 MB storage sizes.    This type has a maximum data transfer rate of 20 MHz with a 10-pin connector type. An Erasure Prevention Switch can set lock to eliminate accidental erasing or recording of data. It also has original serial protocols for compatibility issues. It includes a family of Memory Stick PRO, Memory Stick Duo, Memory Stick Micro (M2) and Memory Stick PRO-HG.
Number 320 - January 2010