A memory or flash card is an electronic data storage device used to store digital information. Used in a myriad of electronic devices including mobile phones, computers, MP3 players, video game consoles and digital cameras, they typically retain data even when the power is turned off.
Rapidly, this technology became ubiquitous, replacing hard disk drives in a variety of applications. Many form factors exist, with NAND and NOR flash memory prevalent in the solid-state nonvolatile memory (NVM) segment. NAND and NOR specify how transistors are connected instead of having them incorporated as part of an FPGA or other logic. With NOR, for example, the flash transistors connect to ground and a bit line for individual bit access, delivering an improved write endurance when compared to NAND flash. NOR flash memory is typically used in MCUs with on-chip flash.
NAND, in comparison, features higher density as the transistors connect in groups to a word line. It is used for block-oriented data storage. The high-capacity data storage platforms where NAND is used incorporate error detection and correction hardware to boost reliability.
Figure 1: A wealth of flash memory cards are on the market in varying sizes, speeds and formats for a wide range of applications. (Source: Time Inc.)
Flash card memory involves three important specs—format, size and speed—with all of the variables divided into classes. Speed, for example, can range from Class 2, the slowest, to Class 10, almost the fastest, outdone only by UHS Class 1 (ultra high speed). An SD card typically measures 32 mm x 24 mm x 2.1 mm and weighs approximately 2 grams.
PNY Technologies’ 4 GB flash memory cards address the security, capacity, environmental and high-performance requirements of consumer electronic devices. Rated Class 4, they are based on an 8-pin interface to operate in a maximum 50 MHz bus clock rate and are used in both portable and stationary applications. The high-voltage microSD memory card voltage range is 2.7-3.6 V. The default variable clock rate is 0-25 MHz, up to 12.5 MB/sec interface speed (using four parallel data lines), and high-speed mode rate is 0-50 MHz, up to 25 MB/sec interface speed (using four parallel data lines). The card’s contact protection mechanism complies with the highest SDMI standard security.
An 8 GB flash memory card from Kingston Technology, the SDC4/8GB is a MicroSDHC card designed to provide video, music, game and photo storage for mobile devices. The size is identical to a standard microSD card spec, but can only be recognized by a microSDHC host device. An included adapter enables this device to be used as a full-size SDHC card. The devices are 100 percent tested and are backed by a lifetime warranty by Kingston.
Panasonic’s RP-SDF02GDA1 is a member of the FX Industrial SLC model family. These SD/SDHC memory cards adopt built-in industrial SLC NAND flash memory and are used in industrial applications where frequent writes are necessary and where large data loads are written. Applications include security camera, factory automation, broadcast equipment and drive recorders. Features include system reliability via powerful error detect and corrective functions, static wear leveling and data recovery at power failure, automatic refresh to prevent uncorrectable errors and bad block management. They comply with SD card specifications.