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Flash Memory, Part I: MMC and SD

MMC and SD 

Flash memory will work with any particular device can be difficult to know is available in so many formats. Such as MP3 players, PDA, mobile phones, digital cameras, personal computers, and devices such as flash memory in order to enhance the storage capacity to take advantage of, but if you select the right type can be easier said than.

The general form of a tip to solve both are very readable, flash memory, so we're doing a two-part series. MMC and SD: Part I of a series of flash memory, similar to the two very popular in general will focus on interchange format.


For more information, before entering some background on each card might be appropriate. Letters 'MMC' in 1997, co-developed by SanDisk and Siemens multimedia card formats stand for one. Secure Digital, a type character 'SD' stand improvement on the original design and the MMC, SanDisk, Matsushita Electronics (Panasonic, better known as), and was jointly developed by Toshiba.

The format is very durable, solid-state (no moving parts) components are protected by a hard plastic shell. Devices typically are not affected by extreme temperatures, shock, without experiencing any damage must withstand a drop of 10 feet.

Physical Characteristics

MMC and SD flash memory device about the size of a postage stamp all general approximatly 24mm X 32mm X 2.1MM measured and the weight of a mere 2g. The small footprint of data about the easiest way to lose to make them, but they also accept that they are small devices can be They get more powerful as personal e-reduction, and the necessary accessories must maintain this speed. Even though they share the same basic form factor, MMC and SD cards are two physical features, sliding tab and the number of connections can be distinguished by.

MMC or SD card label facing, looking for the electrical connections are facing away from you, the notch in the upper right corner of the card will have. Note This is not in the SD card, MMC card at the point on the left edge of the small sliding tab will be. 512MB MMC Card 512MB SD card, and this is compared to a larger image If you look you can see the difference. This tab contains two positions, lock and unlock on the slide. It is the user to manually create a fixed location that can be read from the card means the Data tab on the card to protect your data, but it is not recorded or anything on the card can be removed.

Other physical difference is in the back of the card. 9, whereas the SD card MMC card, seven electrical connections (for data transmission and reception power a small rectangular pad) provides

* While there may be rare exceptions, for all practical purposes, SD and MMC cards "SD / MMC" to indicate the compatibility, especially in the current device can be used interchangeably.

Transfer rate

SD and MMC cards at a slight edge going to the SD card is similar to the data transfer rate. MMC transmission speed in either direction, 9 MB / s SD card, but the peak current 60X (9 MB / s's) Rated speed writing and 66X (10 MB / s's), can be used to read the rated speed. Both vary by quite fast, but the end-user, regardless of the results of type selection, variety and speed does not reach the actual number.

SD and MMC cards, as part of the technical specifications should refer to the speed, it's that you should consider when shopping around is important. Low rate cards are still commercially available, digital camera, or the speed of other devices that may be important and may affect performance. Each speed rating in the 'X' at 45X and 66X compared to you, if you do not feel the big customers rum maybe 10 MB / s compared to the will of 7,425 MB / s is on the side of the load, 0.15 MB / s, represents When referring to a quick card instead of the actual speed grade, and some manufacturers "fast" or "very" and the same word is used.

Note: The "very" or "High Speed" chips before buying the actual write speed of the device to check the specifications of the AMC Gremlin you can put in the Hemi engine, which is not supported by the camera, do not spend the extra money if you ... .


The maximum size SD card that can be used easily with 1GB, 2GB models with up to 4GB of storage capacity of 8 GB model and roads are beginning to show that, SD Card Association state. In contrast, MMC card SD technology to create a much more attractive has a maximum capacity of 512MB.


In the section above mentioned body functions, SD card write-protection benefits. Card 'lock', the users need to unprotect it until you take action to ensure that the data is safe. Inadvertently reduce the risk of data loss or alteration, improve the security of your data on the SD card, MMC card can be removed using.

Although the ability to support other SD MMC contains copyrighted. SanDisk's web site at "Copyright protection for the data encryption security" to refer to this function, and the different position referred to as DRM or digital rights management can be By default, license information, write to the SD card, and it's removed from particular card can not be executed.


In general, the exchange of SD and MMC cards and can be used in compatible devices. In general, the capacity of the SD card, MMC card cost more than, but can be seen in this tip, it offers more for the money.

Many different types of flash media card reader, a general reading and writing skills can be used to promote the personal computer. 15-1 as one reader / writer, 15, MMC and SD two kinds can be read in the same slot on the device, in part to the fact that the audit can be quite dense.

MP3 players to store music files, normally in the memory with the main memory available, but the users in an expansion slot to increase capacity and add their choice of flash memory, the time can be played. Pogo easy scalability RipFlash MP3 player 256MB SD / MMC slot, as well as offering on-board devices.

Mobile Phone and PDA flash memory slot is also thanks to the increased storage space is available. For your convenience, Handspring Treo 600 SD / MMC slot combination that gives the phone / PDA is

Of course, the digital camera is bigger and faster card upgrades are always welcome their 'film' is used as a flash memory. ODAK DX7630 6.1MP 3 times optical zoom, 4x digital zoom, 6.1 megapixel camera megapixel Kodak DX7630 much faster as UMAX AstraPix 640 SD / MMC card to fill, but one of the great things about this card is that the user can select is the size, as well as to meet their specific needs and budget amounts to have on hand.

Warning one word - it can not handle the capacity of the card, make sure the devices. The camera (meaning, depending on the device will be using the camera, 1 GB card and can handle cards up to 512 MB if you use the other hand to the other only, and some even can not read the card. Either you the ability to evaluate) unit card, make sure it matches well. So, as always, you need to purchase a memory that can support the product's documentation to determine.

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