REFERENCE GUIDE FOR FLASH CARDS AND DRIVES Terence O’Kelly Content Links 1. Frequently Asked Questions (FAQs) 2. Introduction to the Reference Guide A. Memorex history A. Differences between analogue and digital recording B. Binary number system used in digital storage 3. Digital storage media C. Capacity chart of digital storage media D. Cost per megabyte comparison of various media E. Solid-state memory chips 1. RAM (Random Access Memory) 2. ROM (Read Only Memory) 3.
I. J. K. L. M. N. O. P. Q. 6. MMCmicro 7. MMCmini 8. SecureMMC 9. miCard Secure Digital 1. SDMI protection 2. MiniSD 3. microSD 4. SDIO cards 5. SDHC Memory Stick 1. MagicGate 2. Memory Stick Duo 3. Memory Stick Pro xD Picture Card Applications of flash cards Comparison of all flash cards 1. Profiles 2.
FAQs about Flash Cards and Drives There is a lot of confusion about the various different types of flash memory. In order to help customers make educated choices about the media and formats they choose, Memorex has assembled a list of Frequently Asked Questions in addition to the Memorex Guide to Flash Cards and Drives that covers the subject in detail. Click on the blue text to get to the answer to each question. Some answers have additional links to the Memorex Reference Guide for even more information.
29) My doesn’t my Memorex TravelDrive show any files on it in Windows 2000 when the write/protect switch is on? They show up in Windows XP. The answers to the questions follow below. Click on the link to the Memorex Reference Guide to Flash Cards and Drives to get more detailed information, including pictures and charts. If you have a question not listed in our FAQs, E-mail the question to us; and we will add your question and the answer to the most frequently asked questions.
13) The problem is a difference in the formatting. When you format your Smart Media in your camera, it is using an older FAT (File Allocation Table) format that goes back to the time when floppy diskettes were the main computer storage medium. Windows XP recognizes that format; but when XP does its own formatting, it defaults to FAT32, a newer file system that cameras do not recognize.
camcorder that is using it in order to keep the file structure perfectly intact. Tip: after reformatting, the camera will automatically number photo files from the beginning, which means new photos will have the same file names and numbers as older photos you may have stored on other media such as hard drives or optical discs. You will have to rename the older or new photos in order to avoid name conflicts if they end up stored in the same file folder.
REFERENCE GUIDE TO FLASH CARDS AND DRIVES Memorex has long been one of the world’s foremost suppliers of media for memory storage. The very name of the company is a shortened form of “MEMORy EXcellence” that started in 1961 with the manufacture of half-inch 9-track computer tape and progressed to audio and video cassettes, digital audio cassettes, and computer diskettes.
ANALOGUE VS. DIGITAL Analogue comes from two Greek words loosely meaning “word for word,” as in a translation. The adjective is a way of describing information in one understandable way analogous to or similar to the actual way. The description is often applied to the use of a “picture for picture” instead of a “word for word” translation. For example, an analogue clock has hands that make a complete circuit in a minute or in an hour or in half a day, depending on which hand it is.
In our familiar decimal system, each column of digits goes up by a factor of 10. The number 3723 is represented by 3,723 with a comma often separating each of the sections worth a thousand. In the binary system that computers understand, 3723 is represented by the number 111010001011 for which each column represents a factor of 2. Each column is twice the value of the column to its right. We count by 10’s (fingers). Computers count by 2’s (on/off transistors).
• • low power requirements to prolonging battery life low cost (Figure 2) Flash memory offers all but the last; but as people become more accustomed to the technology and increasing demand allows production to increase also, costs will continue to decline as they have for the last few years (Figure 2). Costs Per Megabyte cost per megabyte $0.20 $0.18 $0.16 $0.14 $0.12 $0.10 $0.08 $0.06 $0.04 $0.02 $0.
binary terms that is a mere “4.37GB.” Some groups have called for new terminology to define the “kilo binary byte” as a “kibibyte” to distinguish it from a decimal “kilobyte” in order to reduce the confusion. The last column above is the proposed list of new terminology to distinguish binary values. Others, ignoring the heritage of IBM, Greece, and nature’s ten fingers, have claimed the storage industry is cheating the consumer because the computer is always right.
RAM RAM stands for “Random Access Memory.” RAM chips use transistors to link the bit and word lines, and they need a constant energy source to keep the information stored. Once the power source is removed, the transistors lose whatever information was retained until power is restored and new information is sent to the chip. This characteristic is described as “volatile” because the information simply “flies away” once a power supply is removed. ROM ROM is “Read Only Memory.
Finally Flash The development of flash memory solved the problem of slow one-byte-at-a-time erasure of the EEPROMs by using in-circuit wiring across the chip so that either the entire chip could be erased or only selected sections known as blocks. Writing to the chip is also faster because data can transfer at a rate of 512-byte sections instead of the EEPROMs’ slower individual bytes. The links are much the same design as those in EPROMS and EEPROMs— floating gate/oxide layer/control gates.
Figure 5 Comparison of Memory Chips RAM ROM PROM EPROM EEPROM FLASH type of link transistors diode fuse gate gate gate volatile yes no no no no no erasable yes no no yes yes yes loses memory if power is lost inexpensive in large volumes fragile needs UV light for erasure slow erasure and writing expensive but costs are declining Figure 6 Further development of flash memory technology led to these chips appearing in removable cards of different designs and sizes for different applications and USB-based
TRAVELDRIVES —USB PORTABLE MEMORY TravelDrives are not really drives at all since nothing moves inside. They are flash memory devices in the shape of small cartridges no larger than a thumb. One end of the device is a USB connector that plugs into a USB port so that the computer recognizes the device as a removable drive. The fact that the TravelDrive is solid-state memory and not a real mechanical drive means that it is a durable, safe, and reliable means of storing or transferring files.
gives up to NOR logic in quick random access. NOR logic chips are used for applications using binary code rather than memory, such as a computer’s BIOS or a device’s firmware. NAND Flash •Transistors arranged in series •Software allows devices to work similarly to disc NOR Flash • Each transistor stands alone. • Works as internal memory with fast random drives.
the PC cards with their varying thickness, the Type I can fit into all Type II slots, but not vice versa. Although these cards were dubbed “compact” when they were introduced, today they are the largest of the cards most commonly used.
The maximum theoretical capacity of a Compact Flash card is 137GB, but technical problems and costs preclude any move to that capacity any time soon. There is pressure, however, to increase the Compact Flash capacity to 16GB and beyond so that the cards can hold enough data to replace miniDV digital video cassettes in digital camcorders.
SMARTMEDIA Toshiba took a very different approach to flash memory in 1994 when they introduced what they called “solid-state floppy-disk cards” or Smart Media. 5 The card is small, just one-third the size of a credit card and almost as thin because there is no controller chip in the card. The control of data is left to the reading/writing device rather than to the card.
Smart Media chips use just one NAND memory chip in the card. If an SM card needs greater capacity, it simply uses a NAND chip that offers that capacity rather than stack chips as other flash cards do. Smart Media cards also differ from other flash cards in their ability to withstand shocks. Their shock limit is half that of the larger card—1,000 G.s of force versus the Compact Flash limit of 2,000 G.s.
MultiMedia cards operate at either 2.7 volts or 3.6 volts from the power source. These cards will work in Secure Digital card slots as well as MMC slots; but because the SD cards (described below) are slightly thicker, the reverse is not true. Music stored on an MMC card, however, will not play back on an SD device because the SD audio devices only work with encrypted music files. The insertion end of a MultiMedia card has seven gold slide contacts on the back.
USB flash drive available. It is 40% smaller than a miniSD in area and about 18% smaller in volume. Despite the small size, the miCard has a total capacity ranging from 128MB to 8GB with a “theoretical” capacity of 2048GB. That’s 2 terabytes of storage! The miCard uses a 16bit bus rather than the 4-bit or 8-bit buses used in SD and MMC cards, and that 16-bit bus allows sequential speeds of up to 60MB per second with a “theoretical” speed of 120MBs once the internal interface of NAND chips can be sped up.
contributed to SD cards’ greater acceptance in the market than that for the MultiMedia card. Since MultiMedia cards do work in Secure Digital slots, they will not face obsolescence if the format is ever discontinued. The backs of the Secure Digital cards have nine gold slide contacts, two more than those on standard MultiMedia cards.
The SD card has become the most common flash memory card format for electronic products. As a flash card, however, it still has the limitation typical of all flash cards—the need for its own particular card slot in order to be read or be written. USB flash devices owe their enormous popularity to the “universality” of the USB port that is standardized throughout the computer and electronics industry.
SDIO (SD Input/Output) Cards are not flash memory storage devices at all. They are generally mobile electronic devices that plug into ports that are identical to SD ports, but these SDIO cards are designed for many different applications. SDIO cards are completely compatible with the SD format in terms of their mechanical design, electrical and power requirements, signal information, and software parameters.
10) Memory Stick Micro, or “M2” (15mm x 12.5mm x 1.2mm), a tiny version with two low operating voltages of 3.3V or 1.8V to allow their use in very small hand-held devices such as camera phones. The lower 1.8-volt power requirement uses 40% less power than the larger Memory Stick Duo version, an advantage in smaller devices where the greatest weight is in the battery. The MagicGate copy protection is part of the M2 requirements. The first M2 cards come in capacities of 256MB, 512MB, and 1GB.
Flash Card Profiles CompactFlash SmartMedia MMC SD Memory Stick xD Picture Card RS-MMC/ MMCmobile MMCmicro Memory Stick Duo MiniSD microSD M2 Figure 15 As flash media grew in popularity, they found more uses in other devices. MP3 audio players and tiny voice recorders use the smaller flash memory cards as replacements for bulky and unreliable tape cartridges.
speed is always the faster rating because it is easier and faster to pick up data patterns than to sort them and write them. The sizes of files and the number of files, however, will alter the actual speeds. Writing or reading hundreds of small files will take longer than writing or reading the same total capacity spread over several large files.
cells has to be erased first to convert all cells to ones; then the particular cell has to be written again to turn it to a zero. In order to write to a NAND memory chip, the controller must follow a 2-step process: 1. Erase all the cells in a block to ones. 2. Write zeroes to particular cells in a block in order to store digital data. Flash memory is divided into blocks that are generally 128 kB in size, each block holding 64 pages of 2 kB. “Random” writing in NAND memory means: 1.
too low or out of power entirely. Reformatting will return the flash card to use, but reformatting also erases all the information that was on the card. Digital devices such as digital cameras or flash card readers can reformat the cards in a process that is nearly identical to that for floppy disks. Scandisk can also be used to verify the card’s integrity in the same way to be sure the problem was in a corrupt file rather than a damaged card.
• • • • Keep flash cards away from electrostatic sources and magnetic fields. This caution has grown to include sending them through the U.S. Postal Service in the type of packaging that is likely to undergo electron beam irradiation that will damage semiconductors. Do not bend them or drop them. Do not eject the cards or turn off any device when data is being transferred to the card. Be aware of remaining battery power on hand-held devices so that data are not lost if the battery finally runs out.
