Can you tell me what the sd card and mmc card are?

SD card (Secure Digital Memory Card), translated as Secure Digital Card in Chinese, is a new generation of memory device based on semiconductor flash memory. It is widely used in portable devices, such as digital cameras. , personal digital assistant (PDA) and multimedia player, etc. SD card was jointly developed by Panasonic, Toshiba of Japan and SanDisk of the United States in August 1999. The SD memory card is as big as a postage stamp and weighs only 2 grams, but it has high memory capacity, fast data transfer rate, great mobility and good security.

The SD card combines SanDisk flash memory card control and MLC (Multilevel Cell) technology and Toshiba (Toshiba) 0.16u and 0.13u NAND technology in a volume of 24mm×32mm×2.1mm. It passes 9 The pin's interface interface is connected to a dedicated drive and does not require additional power to maintain the information memorized on it. And it is an integrated solid medium without any moving parts, so there is no need to worry about damage from mechanical movement.

The technology of SD card is developed based on MultiMedia Card (MMC) format. It is similar in size to MMC, with dimensions of 32mm x 24mm x 2.1mm. The length and width are the same as MMC, but 0.7mm thicker than MMC to accommodate larger capacity storage units. SD cards and MMC cards remain upwardly compatible. That is to say, MMC can be accessed by new SD devices. The compatibility depends on the application software, but SD cards cannot be accessed by MMC devices. (The SD card adopts a rail-type design with the same thickness as the MMC, so that the SD device can fit into the MMC).

In addition to retaining the 7-pin MMC, the SD interface also adds 2 extra pins on both sides as data lines. It uses NAND type Flash Memory, which is basically the same as SmartMedia, and the average data transfer rate can reach 2MB/s.

SD cards also provide different speeds, which are calculated based on the CD-ROM's 150kB/second rate calculation method. Basically, they are able to transfer up to 6 times faster than standard CD-ROMs (900 kB/sec), while high-speed SD cards are capable of 66x (10 MB/sec) and 133x or more. Some digital cameras require high-speed SD cards to shoot videos more smoothly, and to shoot continuous photos more quickly. As of December 2005, most devices followed the 1.01 specification for SD cards, and devices with higher speeds up to 133x also followed the 1.1 specification.

Devices with SD card slots can use smaller MMC cards, but standard SD cards cannot be inserted into the MMC card slot. SD cards can be used on CF cards and PCMCIA cards by plugging in adapters; miniSD cards and microSD cards can also be used on SD card slots by plugging in adapters. Some USB connectors can plug in SD cards, and some card readers can also plug in SD cards and access them from many ports, such as USB, FireWire, etc.

The structure of the SD card can ensure the security of digital file transmission and is easy to reformat. Therefore, it has a wide range of application fields. Multimedia files such as music, movies, and news can be easily saved to the SD card. middle. Therefore, many digital cameras have begun to support SD cards.

There are many brands of SD cards on the market today, such as: SANDISK, Kingmax, Panasonic and Kingston.

●SD cards produced by SANDISK are the most common ones on the market and are divided into high-speed and low-speed SD cards.

●Kingmax’s SD card adopts unique integrated packaging technology (PIP), making it difficult for counterfeiters to imitate. Kingmax SD card has a maximum transfer rate of 10MB/second, is waterproof, shockproof, and compression-proof. With its three-proof design, it can meet various requirements for outdoor shooting.

●Panasonic SD card, as the creator of the SD standard, its technology can be said to be one of the best SD cards on the market. However, it should be noted that most Panasonic SDs do not have a warranty. When purchasing, be sure to ask the important question of the warranty period.

●Kingston SD card is the smallest among many flash memory products and provides a 5-year warranty.

Use of SD card

SD card is used in the following portable digital devices:

●Digital cameras store photos and videos

● Digital camcorders store photos and videos

●Personal Digital Assistants (PDAs) store various types of data

●Mobile phones store photos, ringtones, music, videos and other data

●Multimedia players

SD cards are mostly used in MP3 players, digital camcorders, digital cameras, etc., and are also used in laptop computers. Its projected area is the same as that of MMC card, but slightly thicker at 2.1mm. However, SD card has a much larger capacity and its read and write speed is 4 times faster than MMC card. At the same time, the SD card interface is compatible with MMC cards, and most interfaces that support SD cards support MMC cards. At present, SD cards are rapidly becoming popular in digital cameras and are likely to become mainstream. SD cards have developed rapidly this year and have begun to threaten the market share of CF cards. This is because the size of SD cards is much smaller than that of CF cards, and the gap between SD cards and CF cards in terms of capacity, performance and price is getting smaller and smaller. In the past two years, mobile phones that support SD cards have rapidly become popular in the market. Therefore, , the rapid growth of SD cards is definitely not accidental. The most important point is that MMC cards are also compatible with SD cards, which is one of the reasons why SD cards have become so popular. However, please note that on some products such as mobile phones, SD cards and MMS cards are not compatible. Current SD card capacities range from 8MB to 4GB.

Identification of SD cards

SD cards are small in size and the average consumer does not know much about them before buying them, so it is difficult to identify them from their appearance. Here is an introduction to the market. How to identify the authenticity of the common SanDisk SD cards: First, look at the memory card itself. Genuine Sandisk memory cards have a laser color-changing label on the front, and the laser color changes at different angles. Secondly, there are genuine licensed cards issued by domestic agents, which are all packaged in a plastic package similar to the one above, but the words "5-year guarantee" and Japanese on the lower right have been changed to a graphic representation of 5-year warranty.

In addition, you can also make the simplest identification based on whether there is a gap at the bottom of the SD card. Since the number above the place of origin on the back of the genuine SanDisk brand SD card is unique, the authenticity can be checked through the 800 phone number, but it is said that This query system is not ready yet.

SD card development history

In 2006, SD card capacities were 8, 16, 32, 64, 128, 256, or 512 MB, 1, 2, 4, 6, 8(SDHC)GB.

SD/MMC card has replaced the SM card developed by Toshiba and has become the most widely used digital memory card format for portable digital cameras. In 2001, the market share of SM cards exceeded 50%, but by 2005 it dropped to around 40%, and is still falling rapidly. Most digital camera manufacturers provide SD card support, including Canon, Nikon, Kodak, Panasonic and Konica Minolta.

The three major manufacturers still insist on using their own proprietary formats: Olympus and Fujifilm use xD cards, and Sony uses Memory Stick.

In addition, SD cards have not yet penetrated the digital SLR camera market where CF cards dominate. (Except Nikon's newly released D50 in 2005 supports SD.)

SD cards are made by Toshiba adding encryption technology hardware to MMC card technology. Since MMC cards may make it easier for users to copy digital music, Toshiba has added these technologies in the hope of providing peace of mind to the music industry. Similar technologies include Sony's MagicGate. In theory, encryption technology can introduce some digital rights management measures, but this feature is rarely used.

Users can use a USB card reader to use the SD card on a personal computer. Some newer computers already have built-in card readers.

The latest development is that SD has a built-in USB port, omitting the card reader. SanDisk's design uses a foldable cover to protect the USB socket. Although Sandisk is not the first SD card manufacturer to have built-in USB functionality, it is due to its important position in the industry. This move led other manufacturers to follow suit.

The "SD" trademark is actually used for a completely different purpose: it was first used on "Super-Density OpticalDisk", a product developed by Toshiba in the DVD format. Lost in the battle. That's why that "D" looks like a compact disc.

SD series memory cards are all submitted to the SD Card Association for certification by SanDisk after completing testing, so almost all patent rights are controlled by SanDisk.

Mini SD and Micro SD card

With the development of SD card storage technology, Mini SD and Micro SD cards gradually appeared.

MiniSD is jointly developed by Panasonic and SanDisk***. In order to facilitate more users to convert mini SD in different memory cards, SanDisk also specially launched an SD adapter card, which can be used with digital cameras, PDAs and MP3 music players that currently use SD cards. . Mini SD is only the size of an SD card, but it has the same reading and writing performance and large capacity as an SD memory card. It is fully compatible with standard SD cards and can be used as a general SD card through the included SD adapter card.

In terms of ultra-small memory card products, the SD Association took the lead in incorporating T-flash into its family and named it Micro SD. Micro SD, which is only as big as a fingernail, amazed consumers after its launch. , this kind of memory card is also used on several MOTO mobile phones. MMC micro and Micro SD are currently the smallest mini memory cards in the world. They are ultra-small but have greater advantages. They can be used in various digital products without wasting space in the internal design of the product, making them popular among product designers. It also plays a role in “fueling the flames” of refined digital life.

Overwrite protection switch

Viewed from above, there is usually a switch on the right side of the SD card, which is the overwrite protection switch, while the MMC card does not. When the overwrite protection switch is turned down, the SD card will be overwrite protected and the data can only be read. When the overwrite protection switch is in the upper position, data can be overwritten. Since this protection switch is selective, some brands of SD cards do not have this protection switch.

The principle of the overwrite protection switch is similar to the overwrite protection on cassette tapes, VHS video tapes, and computer disks. The closed state means that it can be overwritten, and the open state means that it is protected.

If the switch is damaged, the card can only become a write-protected read-only memory card. One way around this is to tape the notch shut so the card will always be writable.

The SD card produced by Kingmax does not have a write-protect switch. Because the company believes the switch is too easily damaged. [2], the SD card it produces has the same thickness as MMC card, which is 1.4 mm.

Open standards

Like other memory card formats, SD cards are protected by numerous patents and registered trademarks, and authorization can only be carried out by the Secure Digital Card Alliance. The Secure Digital Card Alliance's current licensing agreement does not allow open source SD drivers, a situation that has generated a lot of debate about open source and free software. The common approach is to develop an open source shell, but the core is a closed source SD driver for a specific platform. This approach is too different from the expected open standard. Another common approach is to use the older MMC mode, because according to the SD card standard, all SD cards must support MMC mode.

This shows that the openness of SD cards is lower than that of CF cards or flash memory. The above two formats are almost free and only require licensing fees for the use of alliance logos and registered trademarks. But it's much more open than xD cards or memory sticks, which offer no public document support at all.

Technical Notes

All SD and SDIO cards must support the older SPI/MMC mode. This mode supports a slow four-wire serial interface (clock, sequence input, sequence output, chip select) and is compatible with the Serial Terminal Interface (SPI) and many microcontrollers.

Most digital cameras, digital audio players and other portable devices can only use MMC mode. Detailed documentation for this model can be purchased from MMCA for $500. But some documentation about SDIO is free. Some are also available from memory card manufacturers.

MMC mode does not support the encryption feature of the SD card. You can't find these details in the free documentation. But for most consumers, this is of no concern and the user interface is used to store unprotected data.

SD card*** supports three transmission modes: SPI mode (independent serial input and serial output), 1-bit SD mode (independent command and data channel, unique transmission format), 4-bit SD Mode (uses extra pins as well as some reset pins. Supports four-bit wide parallel transfers)

Low-speed cards typically support 0~400 kbit/s data transfer rates using SPI and 1-bit SD transmission mode. The high-speed card supports 0 ~ 100 Mbit/s data transfer rate, using 4-bit SD transmission mode; supports 0-25 Mbit/s, using SPI and 1-bit SD mode.

Manufacturers, vendors and host adapter manufacturers need to pay an SD/SDIO licensing fee of US$1,000 per year plus a membership fee of US$1,500. However, SDIO card and MMC adapter manufacturers do not need licensing fees. The MMC card uses a 7-pin interface, and the SD card and SDIO card use a 9-pin interface.

SDIO Introduction

The SD socket of video lenses using the SDIO interface can be used for more than just inserting memory cards. PDAs, laptops, etc. that support the SDIO interface can be connected like GPS receivers, Wi-Fi or Bluetooth adapters, modems, LAN adapters, barcode readers, FM radios, TV receivers, RFID readers, Or digital cameras and other devices that use SD standard interface.

A number of other devices have also been announced to be supported, including RS-232 serial port adapters, fingerprint scanners, and SDIO to USB master/slave adapters (handheld devices that support the SDIO interface can use USB peripherals or connect to computers ), degaussing readers, Bluetooth/Wi-Fi/GPS radio transceivers, mobile phone modems (Personal Communications Services (PCS), CDPD, GSM, etc.), and APRS/TNC adapters.

Different models of MMC/SD cards

4GB SDHC card SD card is not the only memory card standard approved by the Secure Digital Card Alliance. Other approved formats include miniSD, microSD (called TransFlash before the alliance adopted the standard) and SDHC.

These smaller cards can also be used with a full-size MMC/SD/SDIO slot with an adapter. You must know that it is already very possible to develop an SD-sized input and output device standard, but it is simply unrealistic to develop a smaller size.

The SD slot supports MMC cards, and smaller size MMC card variants are also compatible with devices that support SD cards. Unlike miniSD and microSD, the RS-MMC slot is compatible with full-size MMC cards. Because the RS-MMC card is just a shortened MMC card. For related information, please refer to Multimedia Card (MMC).

In response to the fact that the standard upper limit of SD card capacity is only 4GB, which is not enough to meet the rising capacity demand, the alliance formulated a new SDHC standard. The appearance of an SDHC card is exactly the same as an ordinary SD card, and the lower limit of capacity is 4GB. It is expected that SDHC cards up to 32GB will be launched within the year.

DRM Features

The digital copyright protection solution embedded in the SD card is formulated in accordance with the Content Protection Standard for Recordable Media (CPRM) proposed by 4C. At its core is the use of Cryptomeria (also known as "C2"). This feature is confidential. DVD-Audio discs also use an encryption scheme very similar to CPPM. SD card (Secure Digital Memory Card) is a new generation of memory device based on semiconductor flash memory. SD card was jointly developed by Panasonic, Toshiba of Japan and SanDisk of the United States in August 1999. The SD memory card is as big as a postage stamp and weighs only 2 grams, but it has high memory capacity, fast data transfer rate, great mobility and good security.

SD card is small in size and widely used in digital cameras. It is a brand-new memory card product jointly developed by Japan's Panasonic Corporation, Toshiba Corporation and SanDisk Corporation. Encryption function ensures the security and confidentiality of data. The SD card is consistent in appearance with the MultiMedia Card and is compatible with the MMC card interface specification. However, please note that on some products such as mobile phones, SD cards and MMS cards are not compatible. The price of SD cards is higher than that of MultiMedia Cards with the same capacity.

SD cards are mostly used in MP3 players, digital camcorders, digital cameras, etc. Their projected area is the same as that of MMC cards, only slightly thicker at 2.1mm, but the capacity of SD cards is much larger. And the reading and writing speed is 4 times faster than MMC card. At the same time, the SD card interface is compatible with MMC cards, and most interfaces that support SD cards support MMC cards. At present, SD cards are rapidly becoming popular in digital cameras and are likely to become mainstream. SD cards have developed rapidly this year and have begun to threaten the market share of CF cards. This is because the size of SD cards is much smaller than that of CF cards, and the gap between SD cards and CF cards in terms of capacity, performance and price is getting smaller and smaller. In the past two years, mobile phones that support SD cards have rapidly become popular in the market. Therefore, , the rapid growth of SD cards is definitely not accidental. The most important point is that MMC cards are also compatible with SD cards, which is one of the reasons why SD cards have become so popular.

SD card is suitable for mobile phones

Motorola A920, Motorola A925, Motorola E680, Motorola E680I, Motorola A830, Motorola MPX, Motorola E680g, Motorola A630, Motorola MPX200, Motorola A820, Motorola ROKR E1, Motorola ROKR E2 Motorola L7;

Siemens SX56, Siemens SX1,

Panasonic X300, Panasonic SA7,

Sharp GZ100, Sharp GX32, Sharp 802SH,

BenQ P30, BenQ P50, BenQ P31, BenQ 700,

Samsung SCH-i539, Samsung SCH-i519, Samsung SGH-D700,

Philips 960 , Philips 768, Philips 968,

Sagem myS-7,

Sanyo S103, Sanyo V801S,

Kyocera 7135,

NEC e808,

LG C910,

Amoi M8,

BenQ P30, BenQ P31, BenQ P50, BenQ P51, BenQ S700,

Jite Ztel Ztel

TCL e777

Panda e88, Panda E88, Panda CH860,

Dopod 699, Dopod 535, Dopod 696i, Dopod 700, Dopod 818, Dopod 828, Dopod 515, Dopod 830, Dopod 900, Dopod 696, Dopod 686,

CECT S560, CECT GS900, CECT E2800( ), CECT Mio 8380,

Top S27-708, Top P505

Dibt M7, Dbt M9, Dbt M8,

Daxian CU928,

Lenovo P930, Lenovo ET280, Lenovo ET560, Lenovo ET960, Lenovo ET180, Lenovo XP618,

Sanda SED 8390,

Asus N60,

Haier N60 , Haier M220

GT Giti T200, GT Giti V200, GT Giti G3000, Giti GT G20,

Huawei U636,

Nokia 7710, Nokia 6708,

Mitsubishi M600,

Eastcom ES2100,

Waveguide DOEASY E898

HP HW6515, HP h6365,

Mita 8870, Mitac A700, Mitac A701

Palm Treo 700w, Palm Treo 600, Palm Treo 700p