Flash Cards and Digital "Film" Memory Devices
Flash memory has been around for several
How Flash Memory Works
Flash memory is a type of nonvolatile memory that is divided into blocks, rather than bytes as with normal RAM memory modules. Flash memory, which also is used in most recent computers for BIOS chips, is changed by a process known as
. This process
The speed, low reprogramming current requirements, and compact size of recent flash memory devices have made flash memory a perfect
Types of Flash Memory Devices
Several types of flash memory devices are in common use today, and it's important to know which ones your digital camera is designed to use. The major types include the following:
Some of these are available in different sizes (Type I/Type II). Table 10.28 shows the different types of solid-state storage used in digital cameras and other devices, listed in order of physical size.
Table 10.28. Different Flash Memory Devices and Physical Sizes
CompactFlash was developed by SanDisk Corporation in 1994 and uses ATA architecture to emulate a disk drive; a CompactFlash device attached to a computer has a disk drive letter just like your other drives.
The original size was Type I (3.3mm thick); a
Ironically, SmartMedia (originally known as SSFDC for solid state floppy disk card ) is the simplest of any flash memory device; SmartMedia cards contain only flash memory on a card without any control circuits. This simplicity means that compatibility with different generations of SmartMedia cards can require manufacturer upgrades of SmartMedia-using devices. The Solid State Floppy Disk Forum (www.ssfdc.org.jp/english) oversees development of the SmartMedia standard.
The MultiMediaCard (MMC) was co-developed by SanDisk and Infineon Technologies AG (formerly Siemens AG) in November 1997 for use with smart phones, MP3 players, digital cameras, and camcorders. The MMC uses a simple 7-pin serial interface to devices and contains
A SecureDigital (SD) storage device is
Sony Memory Stick and Memory Stick Pro
Sony, which is heavily involved in both laptop computers and a wide variety of digital cameras and camcorder products, has its own proprietary version of flash memory known as the
Sony Memory Stick
. These devices feature an erase-protection switch, which
Lexar introduced the enhanced Memory Stick PRO in 2003, with capacities
ATA Flash PC Card
Although the PC Card (PCMCIA) form factor is now used for everything from game adapters to modems, from SCSI interfacing to network cards, its original use was computer memory, as the old PCMCIA (Personal Computer Memory Card International Association) acronym indicated.
Unlike normal RAM modules, PC Card memory acts like a disk drive, using the PCMCIA ATA (AT Attachment) standard. PC Cards come in three thicknesses (Type I is 3.3mm, Type II is 5mm, and Type III is 10.5mm), but all are 3.3'' long by 2.13'' wide. Type I and Type II cards are used for ATA-compliant flash memory and the newest ATA-compliant hard disks. Type III cards are used for older ATA-compliant hard disks; a Type III slot also can be used as two Type II slots.
In July 2002, Olympus and Fujifilm, the major supporters of the SmartMedia flash memory standard for digital cameras, announced the xD-Picture Card as a much smaller, more durable replacement for SmartMedia. In addition to being about one third the size of SmartMedia ”making it the smallest flash memory format yet ”xD-Picture Card media has a faster controller to enable faster image capture.
Initial capacities range from 16MB up to 128MB, but eventual capacities are expected to reach up to 1GB or above. 16MB and 32MB cards (commonly packaged with cameras) record data at speeds of 1.3MBps, whereas 64MB and larger cards record data at 3MBps. The read speed for all sizes is 5MBps. The media is manufactured for Olympus and Fujifilm by Toshiba, and because xD-Picture media is optimized for the differences in the cameras (Olympus's media supports the panorama mode found in some Olympus xD-Picture cameras, for example), you should use the same brand of camera and media.
USB Keychain Drives
As an alternative to floppy and Zip/SuperDisk-class removable-media drives, USB-based flash memory devices are
Unlike other types of flash memory, USB keychain drives don't require a separate card reader; they can be plugged into any USB port or hub. Although a driver is usually required for Windows 98 and Windows 98SE, most USB keychain drives can be read immediately by newer versions of Windows, particularly Windows XP. As with other types of flash memory, USB keychain drives are assigned a drive letter when connected to the computer. Most have capacities ranging from 32MB to 128MB, with some capacities as high as 2GB. However, typical performance is about 1MBps.
If you have a card reader plugged into a USB hub or port on your computer, you might need to disconnect it before you can attach a USB keychain drive. Use the Windows Safely Remove Hardware icon in the system tray to stop the card reader before you insert the USB keychain drive. After the USB keychain drive has been recognized by the system, you should be able to reattach the card reader.
For additional protection of your data, some USB keychain drives have a mechanical write-protect switch; others include or support password-protected data encryption as an option, and some are capable of being a bootable device (if supported in the BIOS). The Kanguru MicroDrive+ can be upgraded with SD or MMC flash cards for additional capacity.
Figure 10.22 shows the features of a typical USB keychain drive, the NexDisk USB storage device from Jungsoft.
Figure 10.22. The Jungsoft NexDisk USB storage device holds 128MB of data, which can be write-protected to help prevent accidental erasure.
Comparing Flash Memory Devices
As with any storage issue, you must compare each product's features to your needs. You should check the following issues before purchasing flash memory devices:
Only the ATA Flash cards can be attached directly to a laptop computer's PC Card slots. All other devices need their own socket or some type of adapter to transfer data.
Figure 10.23 shows how the most common types of flash memory cards compare in size to each other and to a penny.
Figure 10.23. SmartMedia, CompactFlash, MultiMediaCard, Secure Digital, xD-Picture Card, and Sony Memory Stick flash memory devices. Shown in maximum capacity versions and in relative scale to a U.S. penny (lower right).
Table 10.29 provides an overview of the major types of flash memory devices and their capacities.
Table 10.29. Flash Memory Card Capacities
I normally recommend devices (cameras, PDAs, and so on) that use CompactFlash (CF) or Secure Digital (SD) storage. Any of the others I
CompactFlash (CF) is the most widely used format in professional and consumer devices, and it offers the highest capacity, at the
Secure Digital (SD) is becoming more popular, is reasonably fast, and available in capacities up to 1GB. SD sockets also take MultiMediaCards (MMCs), which are basically a thinner version of SD. Note that the
In general I would not consider any device that used the other formats,
Moving Data in Flash Memory Devices to Your Computer
Several types of devices can be purchased to enable the data on flash memory cards to be moved from digital cameras and other devices to a computer. Although some digital cameras come with an RS-232 serial cable for data downloading, this is a painfully slow method, even for low-end cameras with less than a megapixel (1,000-pixel horizontal width) resolution.
The major companies that produce flash card products sell card readers that can be used to transfer data from proprietary flash memory cards to PCs. These card readers typically plug into the computer's USB ports (some older versions might use the parallel port) for fast access to the data on the card.
In addition to providing fast data transfer, card readers enable the reuse of expensive digital film after the photos are
Because many computer and electronics device users might have devices that use two or more types of flash memory, many
Figure 10.24. The SanDisk ImageMate 8 in 1 Card Reader/Writer is a high-speed USB 2.0 device that can read CompactFlash Type I/II, Memory Stick, Memory Stick Pro, SmartMedia, xD-Picture Card, Secure Digital, and MultiMediaCard formats.
Type II PC Card Adapters
For use in the field, you might prefer to adapt flash memory cards to the Type II PC Card slot. You insert the flash memory into the adapter; then, you slide the adapter into the laptop computer's Type II PC Card slot. Figure 10.25 shows how a CompactFlash card Type II PC Card adapter works. As with card readers, check with the major companies that produce your type of flash memory device for the models available.
Figure 10.25. A typical Type II PC Card adapter for CompactFlash media (left) compared to an ATA DataFlash card (right).
If you have a standard 3 1/2'' floppy drive connected to a standard floppy controller, you have a third alternative for reading the contents of flash memory cards: SmartDisk (www.smartdisk.com) makes the FlashPath line of flash memory card adapters that fit in place of a 3 1/2'' floppy disk. Separate models are available for SmartMedia, Sony Memory Stick, and CompactFlash cards. As shown in Figure 10.26, the flash memory devices are inserted into the FlashPath adapter. Then, the FlashPath adapter is inserted into a 3 1/2'' floppy drive.
Figure 10.26. A CompactFlash module is inserted into the FlashPath adapter; the assembly is then inserted into a standard 3 1/2'' floppy drive. (Photo