MMC memory card description. Computer help

No sooner had we gotten comfortable with cards that comply with the SD 1.1 specification (and most devices still only support the slower SD 1.0), when the transition to SD 2.0 loomed on the horizon. It can be assumed that, as a result, 1.1 becomes a “passing” version, and you should not pay attention to it. In reality everything is different. There are feelings that the implementation of SD 2.0 will be even slower and more painful than the transition from 1.0 to 1.1 or even from MMC 3.0 to 4.x. Most likely, this process will resemble the transition from MMC to SD, which, by the way, never ended - instead of the death of MMC, which was repeatedly predicted (including by me), this format, on the contrary, recently found a second wind. The reason is the same - lack backward compatibility SD and SDHC (all cards that meet 2.0 specifications will wear this logo). If an SD 1.1 card can be safely used in conjunction with devices designed for SD 1.0 (albeit at a lower speed - as much as was possible in 1.0), the same applies to MMC 4.x/3.0, then the SDHC card will work “normally” There will be no SD device. Thus, an SD 1.1 or MMCplus card could be purchased for the future, but an SDHC card could not. At the same time, SDHC devices will be compatible (when available) with regular SD cards, so you can safely purchase the latter. It is not a fact that you will lose something later. Why? Let's see what SD 2.0 will bring us.

Just working on some bugs

The transition from SD 1.0 to 1.1 doubled the maximum operating speed, the transition from MMC 3.0 to 4.0 essentially gave us new cards, but what does SD 2.0 give? Officially, there are only two things - increasing the maximum capacity of cards and the Class Speed ​​Rating. The second one is easier, so let's start with it.

As you know, manufacturers prefer to mark memory cards according to their maximum reading speed, and according to what is theoretically possible. Not all and not always, but in most cases this is exactly what we observe. If the recording speed is indicated, it is also the maximum, and even then not always, and only in the specifications and in small print. And the reading speed (the notorious “X’s”) is most often indicated directly on the card in arshin (compared to the size of the card itself) letters. However, it is not always at least close to the write speed (a striking example is MLC chips, where the difference is several times by definition), and it is difficult to achieve high values ​​of the latter in the case of flash. Manufacturers do not indicate it - it is unprofitable. As a result, the purchased “high-speed” card can easily turn out to be slower than the “regular” one, which we have encountered more than once. At the same time, in many areas of application, reading speed is not very important (just think - photos after a vacation will be transferred to the computer in 10 minutes, and not in 5: no one will die), while writing speed is critical. An example is the same cameras, where low recording speed simply does not allow continuous shooting. The situation is even worse with video recording, where flash is gradually becoming one of the most commonly used media: low recording speed will make shooting simply impossible due to the fact that most frames will “drop out” with an obvious end result. The first attempt to sort out the labeling mess was made by the MMC Alliance: the MMCplus card must not only support the 4.x specification, but also have a minimum sustained write speed of at least 2 MB/s. The SD Association went even further by introducing three classes of cards: Class 2, Class 4 and Class 6. The numbers here are not abstract values, but the established minimum write speed - 2, 4 and 6 MB/s. The innovation is useful, but not so vital: our tests show that today the vast majority of even inexpensive cards are quite capable of handling a flow of 6 MB/s. On the other hand, it will become easier when purchasing: for example, if you know that SDHC Class 6 is required to fully realize the capabilities of a photo or video camera, then you should look for such a card without rummaging through test results and descriptions on manufacturers’ websites. Of course, the possibility of abuse by the manufacturer remains theoretical, but in this case he will receive not only sorrowful lamentations from the deceived user on various forums, but also persecution from the Association, which is unlikely to happen to anyone (even from small companies).

As for volume, the situation here is simple and clear. Officially, the capacity of today's SD cards cannot exceed 2 GB. The limitation is not physical, but logical: the reason for this is the file system used - FAT16. The latter also supports volumes larger than 2 GB, but with a non-standard cluster size, which most manufacturers of household equipment will not do. And for SDHC official file system is FAT32, so the restriction is almost lifted. However, some upper limits are still included in the standard - 32 gigabytes, but compact cards still have to grow and grow to reach such a capacity (and prices fall and fall :)). In the end, some of the formats support larger volumes, but cards with at least 16 GB, let alone 32 or 64, are not yet visible;) Thus, from this point of view, SDHC are an obvious step forward compared to SD . However, it is somewhat blurred by the fact that some equipment manufacturers have already mastered support for FAT32 within SD 1.1. And memory card manufacturers responded to this by releasing SD cards with a capacity of 4 gigabytes. Such cards, even in our area, already cost less than $100. They will subsequently work in devices with SDHC support (let me remind you that there is compatibility in this direction), but no one will fix devices that do not support such cards anyway, since SDHC will definitely not work in them;)

This is what makes the transition from SD 1.1 to 2.0 different from the transition from 1.0 to 1.1. In the second case, we could simply purchase new cards and wait for new devices to appear that would reveal all their capabilities. In the first place it is necessary at first wait for the market to become saturated with devices that support SDHC, and Then buy cards because they are useless for older devices. And even then, you can still use regular high-capacity SD cards, since they will work in the future. It is possible that in the present, but this specific device needs to be checked. So far, on the SanDisk website I have found only seven SDHC-compatible devices with all that it implies. We can say that those actively announced in Lately SDHC cards with a capacity of 4 GB are simply useless - you can buy a regular one of this capacity. When you want to get an eight-gigabyte card, it’s a different matter: there will be no SDHC alternatives. But first you need to purchase a device in which you can use such a card.

How can this affect “popular” volumes up to 2 GB? No way - SDHC cards of such capacity are not planned. This market segment will remain the domain of SD 1.1, but many users at the current price level don’t even need two gigabytes. This is why testing SD 1.1 cards continues to make sense, and this situation can last at least another year, or even more. The MMC Alliance, after the appearance of version 4.1 specifications, does not make any sudden movements - first you need to master what the standard already allows (fortunately, the latest version of the specification was developed a little later than in the case of a competitor, and was much more revolutionary than SD 1.1 - in As a result, completely standard MMC 4.x cards with a capacity of 8 GB have already been announced, and nothing had to be changed in the standard;)). Our main interest for now continues to be cards compatible with SD 1.1 and MMC 4.1. These are the ones we will study again. The topic of today's article is representatives of several lines of flash cards from Kingston, which belong specifically to the two families mentioned. In addition to the manufacturer, they are also related, by the way, by capacity - all gigabytes. For many applications it is quite enough, and the price has already dropped to such a level that you don’t have to deny yourself anything;)

Getting to know the subjects

According to the chronology of creation and the alphabet, it is most logical to start with MMCplus - a direct descendant of those good old MMC cards, with a capacity of a dozen or two megabytes, from which all branches of the family tree of both MMC and SD families began their “pedigree”. But the rest are essentially lateral shoots, and MMCplus, I repeat once again, is direct, although in its content (and a little in form - the contact group is completely different) significantly different from its ancestor. However, we have seen a lot of cards of this standard, so I’ll tell you that its real capacity, according to Everest, is 973 megabytes, and let’s move on.

MMC cards were originally designed to be as compact as possible, but time has shown that they are too large for some applications. A new shoot sprang from the tree - RS-MMC cards, which looked like they were cut to the length of the MMC. Later, DV RS-MMC appeared on their basis, characterized by support for supply voltage not only 3.3 V, but also 1.8 V - since energy consumption is directly related to voltage, the need to reduce it in mobile devices ah obvious. And after the appearance of the MMC 4.0 specifications, MMCmobile - DV RS-MMC with support for new operating modes was released. If you look from the other side, you can call these cards RS-MMCplus, fortunately, for full-size models it is also recommended (albeit optional) to support a voltage of 1.8 V. At first, all RS modifications were noticeably inferior in capacity to the base ones (for purely technical reasons ), however, as technology develops, prices for high-density flash chips fall and user appetite grows (mobile phones, where such cards are in use, have long been competing with digital players with considerable success and are getting closer and closer to the domain of “digital point-and-shoot cameras”), the gap in the case mass modifications were increasingly reduced. However, I have not yet seen the announcement of MMCmobile for 8 GB, and MMCplus - no problem, but in the retail network (at least in Moscow) both cards are still limited to two gigabytes. We, as I said, are testing a card with a declared capacity of 1 GB or (according to Everest) 988 MB of real capacity.

The Secure Digital standard evolved from MMC quite a long time ago, and is not its direct descendant - the cards are similar, but, strictly speaking, they do not have to be compatible in any direction (however, thanks to manufacturers of household equipment, we can often use both, but This is achieved using two-standard controllers). Nominally, two versions of the specifications have changed (and they existed for different times), but, as I wrote at the beginning of the article, version 1.1 will not disappear anywhere in the near future, and cards up to 2 GB will not disappear anywhere. We are testing just a gigabyte card, and not a simple one, but an “extreme” one. However, from Kingston’s point of view, the speed limit is at 133x, and some manufacturers have mastered 150x, but the latter in practice can mean anything, and the promised 20 MB/s at least for read operations is now quite real. Tests will show how real they are in our case. Let me just say that the attempt to achieve technical perfection and create cards that are universal for all applications has played a bad joke on Secure Digital: virtually no one uses this very secure card, and it eats up the card’s capacity. According to Everest, Kingston's GB SD card has a capacity of only 941 MB.

The use of flash cards in small-sized equipment, as I said, led to the flourishing of their smaller modifications. If the MMC Alliance focused on RS-MMC/MMCmobile, then the alternative from the SD Association was miniSD cards. It is worth noting that the Alliance’s position is slightly better - in the case of MMC, the cards are physically and electrically compatible in terms of connector. The SD Association did not cut it, but came up with a new form factor that is compatible with the “ancestor” only with the help of special adapters. And so the features are the same - reduced size and reduced supply voltage. The capacity was reduced for a long time, but now both SD and miniSD are equally limited by the limitations of the standard, that is, 2 gigabytes (in practice, however, there is a difference - “non-standard” cards with twice the capacity in the case of SD exist, but no one makes such miniSD didn't risk it). By the way, the real capacity, the funny thing is, in our case, miniSD has more: 949 MB according to Everest :)

And now we will measure your boy- the hero of one cult cartoon used to say. Maps, of course, are not boys (and not girls either :)), and I am not postman Pechkin, but without measurements in our time, there’s no place either.

Testing methodology

Testing was carried out on a computer with the following configuration:

• EpoX 8NPA SLI
• AMD Athlon 64 3200+ (512K L2)
• 1 GB PC3200 DDR SDRAM
• system hard drive Western Digital WD740GD
• Apacer MegaSteno AM230 card reader
• Windows XP Pro+SP2

To measure the parameters of the subjects, the Lavalys Everest program was used Ultimate Edition 2006 2.80, or rather, the test of disk drives included in it.

Competitors

Since our cards are of different standards, the diagrams will show everything that we have previously tested on this card reader. At the same time, among other things, we will once again compare the capabilities of MMC 4. x and SD 1.1 with each other: nevertheless, we haven’t tested enough of them yet to deny ourselves the pleasure :)

Reading tests

In this case, no one managed to repeat the record of the ultra-fast MMCplus card from Apacer. Kingston MMCplus, judging by the results, supports only four data lines and a mandatory (from the point of view of the standard) synchronization frequency of 26 MHz. MMCmobile is noticeably faster (most likely due to the utilization of the entire possible bus width), but does not reach high-speed SD cards. But both SD and miniSD cards quite achieve the required speed of 133x, despite the fact that no one has declared record performance for the latter.

Read access time for most cards has long been within the range of 0.5-1.5 ms. Our current subjects were no exception. It can be regarded as a funny grimace of fate that their results are arranged in alphabetical order, despite the alternation of formats in it :)

Recording tests

miniSD is noticeably behind the full-size card, although it works very quickly. SD showed exactly the same result as 133x from Pretec - sometimes, it turns out, you can pay attention to the “X’s”. In the MMCplus/MMCmobile pair, the positions have changed: judging by the speed, the second card uses MLC chips with all that that implies. And for the first, the read and write speeds do not differ, which works in favor of the theory about the narrowness of the data bus - the flash microcircuits themselves would “use” even more, but they are not given it.

With one exception, access times for write operations are as expected. However, an exception is worthy of special mention: the write access time for SD Ultimate is lower than for the fastest hard drives, although for most flash drives the opposite picture is observed (as can be seen in the diagram). This result is not unique - the Pretec i-Disk Diamond flash drive also “responds” quickly. At this rate, soon all flash drives will outperform their magnetic counterparts in all performance parameters;) It would be nice to solve the problem with a limited number of rewrite cycles, reduce the price and that’s it - solid-state drives will play the funeral march for their competitors :)

Real Capacity

I indicated it above (in the description of the cards), but for ease of comparison I will repeat it in the table:

What conclusions can be drawn? Firstly, you shouldn’t count on the declared capacity - the real one is noticeably less. Secondly, even within the framework of the products of one company of the same standard, they can differ significantly. Thirdly, what I paid attention to is that, all other things being equal, the capacity of MMC cards is higher than that of SD cards: nothing comes for free in this world. The difference between the minimum and maximum in today's testing reaches 47 MB ​​- quite recently, cards with a lower total capacity were a very popular product (smaller ones are still often included in camera kits) ;)

Prices

The table below shows the average retail prices of the cards tested today in Moscow, current at the time you read this article:

MMCplus	MMCmobile	Secure Digital	miniSD
N/A(0)	N/A(0)	N/A(0)	N/A(0)

Total

Not long ago we became convinced that MMC cards can be much faster than SD cards. Today we saw not the first confirmation that they are not always faster, even in ideal conditions. In old equipment, everything will be even worse for MMC - high-speed SD can lose speed twice as much, while high-speed MMC can “sag” by more than an order of magnitude.

As for the Kingston cards themselves, they all demonstrate very decent speed performance, even when they didn’t promise this (when they promised, the reality lives up to the promises). However, they differ at an affordable price, which, coupled with the popularity of this brand and a good warranty period, makes them a very reasonable candidate for purchase. All. Which ones exactly depend on your preferences (or rather, the preferences of your digital equipment) in terms of buses and form factors.

As can be seen from the figure, after transmitting the command frame, it is necessary to continue reading bytes (Ncr) from the microSD until receiving a response (R1), while the CS level must be active "0".

Depending on the command index, the answer may be not only R1(see set of basic commands) on CMD58 answer R3(R1 and the terminating 32-bit OCR value), and some commands require more NCR time and will respond R1b. This is the R1 response, followed by a busy flag (the signal on the "DO" line is held low by the card while the internal process continues). The host controller must wait for the process to complete until "DO" goes high (ie wait for 0xFF). And also R2 when requesting the status of the STATUS register.

The response R1 contains 1 byte, its structure can be seen in the table below. The response R2 consists of two bytes, the first byte is R1 and the second is R2 (see R2 structure table). And the answer R3 is respectively 5 bytes.

Response R1 with value 0x00 means the command completed successfully, otherwise the corresponding flag will be set.

Structure of answer R1.

R2 response structure.

Initialization in SPI mode.

After a reset and power supply, the card is by default set to operating mode using the MMC (Serial Peripheral Interface) protocol; to switch to SPI mode, you must do the following:

1. After reaching 2.2 V, wait at least a millisecond, set the DI and CS lines high and issue about 80 pulses to the CLK pin. After this procedure, the card will be ready to accept the home team.
2. Send command CMD0 (soft reset). The card must respond (R1) with the wait bit set (0x01).
3. Send command CMD1 (to start initializing the card). Wait for response 0x00 to confirm process completion initialization.

Let me remind you that the CMD0 command must contain the correct CRC field. There is no point in calculating, since there are no arguments in this command, so it is constant and has the value 0x95. When the card will go in into SPI mode, the CRC function will be disabled and will not be checked. The CRC option can be re-enabled with CMD59.

As a result, the CMD0 command will look like this: 0x40.0x00.0x00.0x00.0x00.0x95.

• team index - 0x40.
• argument - 0x00.0x00.0x00.0x00.
• CRC-0x95.

As for 80 pulses, they can be generated by transmitting the value 0xFF via SPI10 times in a rowat high levels set on the lines DI and CS.

After being idle for more than 5 ms, the memory card goes into power-saving mode and is only able to accept CMD0, CMD1 and CMD58 commands. Therefore, the initialization process (CMD1) must be repeated almost every time when reading/writing a data block or checking the status of the card.

For SDC cards if the command is rejectedCMD1 is recommended to use the ACMD41 command.

The initialization process itself can take a relatively long time (depending on the size of the card) and can reach hundreds of milliseconds.

Reading and writing a data block.

By default, in SPI mode, exchange between the microcontroller and the card is carried out in blocks of 512 bytes, so to write even one byte you will have to first read the entire block and, by changing the byte, rewrite it back. The block size can be changed in the CSD register of the memory card.

To avoid addressing errors when executing read/write commands, it is necessary that the address be clearly indicated at the beginning of the sector. To do this, you can reset bit “0” of 3 bytes of the sector address, i.e. make it even, and the minor one should always have the value 0x00.

Reading a data block.

The algorithm for reading a data block is as follows:

• After confirming initialization, we transmit the command CMD17 (response R1), with the address of the required sector.
• We transmit 0xFF before receiving the start byte 0xFE.
• We accept a data block (512 bytes by default) and 2 bytes of CRC.

The CRC value is not required, but the acceptance procedure (transfer of 0xFF from the MK) is necessary.

Reading block.

Write a data block.

The algorithm for writing a data block is as follows:

• If the card was idle for more than 5 ms, send the CMD1 command (response R1).
• After confirming initialization, we transmit the CMD24 command (response R1), with the address of the required sector.
• We transmit the start byte 0xFE.
• We transmit a data block (512 bytes by default) and 2 bytes of CRC.
• We receive the write confirmation byte.
• We are waiting for the end of recording (change of byte 0x00).

The data block can be smaller than 512 bytes when changing the block length with the CMD16 command.

The CRC value is not required, but the procedure for passing any values ​​is necessary.

You can not do the downtime assessment programmatically, but immediately issue an initialization command. During the software implementation I encountered an incorrect recording, for some reason all the bytes were written to a left-shifted sector. The problem was solved only by transmitting the start bit (0xFE) twice.

Block recording.

Acknowledgment byte when writing a data block.

Write/read several blocks in a row.

Using commands CMD18, CMD25 you can read/write several blocks in a row or the so-called multi-block read/write. If the number of blocks has not been specified, the reading/writing process can be stopped using CMD12 commands during reading, as well as by passing the " Stop Tran" when recording accordingly.

Practical use.

The practical use of memory cards is quite wide. In his latest design, he used microSD to record readings from various sensors (temperature, alarm) throughout the day every hour. Data is saved as follows:

• The year is taken from the last two digits - this corresponds to the first (main) byte of the memory card sector address.
• Month, two digits - this corresponds to the second, most significant byte of the memory card sector address.
• Day, two digits are multiplied by 2 (to avoid hitting outside the sector boundary) - this is the third, middle byte of the memory card sector address.
• The low-order, fourth byte is always "0".

As a result, searching for data by date is simplified; you just need to translate the request to the sector address and read from the card. With this method, data can be stored for several years. True, there are also disadvantages; there is a lot of unused space left. Although, if desired, you can use it for other tasks.

Who needs it, I’ll send you a code fragment in assembler for 18 peaks.

Questions can be asked at..

MultiMediaCard, officially abbreviated MMC, is a memory card standard used for solid-state storage. Introduced in 1997 by SanDisk and Siemens AG, GCIs are based on a surface-contact, low-pin-count serial interface, using a substrate stack node of a single memory block, and are therefore much smaller than previous systems based on high pin-count parallel interfaces with using traditional surface-mount assemblies such as CompactFlash. Both products were originally introduced using SanDisk NOR based flash technology. MMC about size postage stamp: 24 mm × 32 mm × 1.4 mm. MMC originally used a 1-bit serial interface, but newer versions of the specification allow the transfer of 4 or 8 bits at a time. MMC can be used in many devices that can use Secure Digital (SD) cards.

Typically, the MMC functions as a storage medium for a portable device, in a form that can be easily removed for computer access. For example, a digital camera will use MMC to store image files. Through an MMC reader (typically a small box that connects via USB or some other serial connection, although some may be found integrated into the computer itself), the user can transfer pictures taken with a digital camera to his or her computer . Modern computers, like laptops and desktops, often have SD slots that can optionally read MMS if the operating system drivers can.

KMMs are available in sizes up to 512 GB. They are used in virtually all environments in which memory cards are used, such as cell phones, digital audio players, digital cameras and PDAs. Since the introduction of SD cards, several companies have been building MMC slots into their devices (the exception being some mobile devices, such as the Nokia 9300 Communicator in 2004, where the smaller size of the MMC is an advantage), but slightly thinner, pin-compatible MMCs can be used virtually Any device that can use SD cards if the software/firmware on the device is capable.

While some companies are building MMC slots into the device as of 2018 (SD cards are more common), embedded MMC (EMMC) is still widely used in consumer electronics as the primary means of integrated storage in portable devices. It provides a low-cost flash memory system with a built-in controller that can reside inside an Android or Windows phone or in a low-cost PC and can appear on the host as a boot device, instead of a more expensive form of solid-state storage such as a traditional solid-state drive.

Open standard

The best of four types of MMC cards (clockwise from left to right): MMC, RS-MMC, MMCplus, MMCmobile, metal extender

The bottom is four cards

This technology is a standard available to any company wishing to develop products based on it. There are no royalty charges for devices that accept MMC. Membership in the MMC Association must be purchased in order to produce the cards themselves.

As of July 2009, specification version 4.4 (dated March 2009) can be requested from the MMCA, and after registration with the MMCA, can be downloaded for free. Older versions of the standard, as well as some additional enhancements to the standard such as MiCard and SecureMMC, must be purchased separately.

Very detailed version is available online which contains the necessary information to write an MMC driver.

As of September 23, 2008, the MMCA team has already rolled out all specifications in the JEDEC organization including implemented MMC (electronic MMC) and miCARD assets. JEDEC is the standards organization for the solid state industry.

As of February 2015, the latest version of the 5.1 specification can be requested from JEDEC, and after registering with JEDEC, a free charge can be downloaded. Older versions of the standard, as well as some additional enhancements to the standard such as MiCard and SecureMMC, must be purchased separately.

Options

RS-MMC

In 2004 reduced size MultiMediaCard (RS-MMC listen)) was introduced as a smaller MMC form factor, about half the size: 24 mm × 18 mm × 1.4 mm. RS-MMC uses a simple mechanical adapter to extend the card so it can be used in any MMC (or SD) slot. RS-MMC is currently available in sizes up to 2 GB.

The modern continuation of RS-MMC is commonly known as Minidrive (MD-MMC). Minidrive is usually a MicroSD card adapter in the RS-MMC form factor. This allows the user to take advantage of the wider range of modern MMCA available to exceed the historical 2 GB limitation of older chip technology.

Version 4.x maps full size and reduced size maps may be sold as MMCplus And MMCmobile respectively.

The 4.x version of the card is fully backwards compatible with existing readers, but requires updated hardware/software to take advantage of its new capabilities; Even though the four-bit wide bus and high-speed operating modes are intentionally electrically compatible with SD, the initialization protocol is different, so firmware/software updates must use these features in the SD reader.

MMCmicro

MMCmicro micro-sized version of MMC. With dimensions of 14mm x 12mm x 1.1mm, even smaller and thinner than RS-MMC. Like MMCmobile, MMCmicro allows dual voltage, is backward compatible with MMC, and can be used in full-size MMC and SD slots with a mechanical adapter. MMCmicro cards have high speed and four-bit buses features the 4.x specification, but not an eight-bit bus, due to the lack of additional pins.

Previously she was known as S-card when introduced by Samsung on December 13, 2004. It was later adapted and introduced in 2005 by the MultiMediaCard Association (MMCA) as the third form factor memory card in MultiMediaCard family.

MMCmicro looks very similar to MicroSD, but the two formats are not physically compatible and have incompatible layouts.

MiCard

MiCard is a backwards compatible extension of the MMC standard with a theoretical maximum size of 2048 GB (2 TB) announced on June 2, 2007 the card consists of two detachable parts, the same as MicroSD cards with SD adapter. The small memory card fits directly into a USB port and also has MMC-compatible electrical contacts, which with the included electromechanical adapter fits in traditional MMC and SD card readers. To date, only one manufacturer (Pretec) has released cards in this format.

Taiwan development, at the time of the announcement, twelve Taiwanese companies (including ADATA Technology, Asustek, BenQ, Carry Computer Eng. Co., C-One Technology, DBTEL, Power Digital Card Co. and RiCHIP) signed a manufacturing contract new card memory. However, as of June 2011, none of the listed companies have released any such cards, and no further statements have been made about plans for the format.

The card was announced available beginning in the third quarter of 2007, it was expected to save 12 Taiwanese companies that planned to manufacture the product and associated hardware up to US$40 million in licensing fees that would presumably otherwise be paid to owners of competing flash memory formats. The original card was supposed to have a capacity of 8 GB, while the standard would have allowed sizes up to 2048 GB. It was stated to have a data transfer rate of 480 Mbit/s (60 MB/s), with plans to increase capacity over time.

SecureMMC

An additional, optional part of the MMC 4.x specification is a DRM mechanism designed to allow MMC to compete with SD or Memory Stick media in this area. Very little information is known about how SecureMMC works or how its DRM characteristics compare it to its competitors.

EMMC

The EMMC (embedded MMC) architecture puts an MMC (flash memory plus controller) component into a small ball-package grid array (BGA) IC for use in printed circuit boards as an embedded non-volatile memory system. EMMC exists in 100, 153, 169 ball packs and is based on an 8-bit parallel interface. This is noticeably different from other versions of the MMC, as it is not a removable card user, but rather a permanent attachment to the circuit board. In case of any issue arising from any memory or controller, the entire PCB (Printed Circuit Board) will need to be replaced.

EMMC does not support SPI protocol buses.

Almost all mobile phones and tablets used this form of flash for primary storage until 2016, in 2016 UFS began to take control of the market. Latest version The EMMC standard (JESD84-B51) by JEDEC is version 5.1 released in February 2015 with speeds rivaling discrete SATA-based solid-state drives (400 MB/s).

other

Seagate, Hitachi and others are in the process of releasing SFF hard drives with an interface called CE-ATA. This interface is electrically and physically compatible with the MMC specification. However, the command structure has been extended to allow the host controller to issue ATA commands to control the hard drive.

Table

Type	MMC	RS-MMC	MMCplus	MMCmobile	SecureMMC	SDIO	SD	MiniSD	MicroSD
SD connector compatible	Yes	filler	Yes	filler	Yes	Yes	Yes	adapter	adapter
Pins	7	7	13	13	7	9	9	11	8
width	24 mm	24 mm	24 mm	24 mm	24 mm	24 mm	24 mm	20 mm	11 mm
length	32 mm	18 mm	32 mm	18 mm	32 mm	32 mm +	32 mm	21.5 mm	15 mm
thickness	1.4 mm	1.4 mm	1.4 mm	1.4 mm	1.4 mm	2.1 mm	2.1 mm (maximum) 1.4 mm (rare)	1.4 mm	1 mm
1-bit SPI bus mode	Optional	Optional	Optional	Optional	Yes	Yes	Yes	Yes	Yes
SPI bus frequency Max	20 MHz	20 MHz	52 MHz	52 MHz	20 MHz	50 MHz	25 MHz	50 MHz	50 MHz
Mode 1-bit MMC/SD bus	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Mode 4-bit MMC/SD bus	No	No	Yes	Yes	No	Optional	Yes	Yes	Yes
8-bit MMC bus mode	No	No	Yes	Yes	No	No	No	No	No
DDR mode	No	No	Yes	Yes	unknown	unknown	unknown	unknown	unknown
Max MMC/SD bus frequency	20 MHz	20 MHz	52 MHz	52 MHz	20 MHz?	50 MHz	208 MHz	208 MHz	208 MHz
Max MMC/SD data transfer rate	20 Mbit/s	20 Mbit/s	832 Mbit/s	832 Mbit/s	20 Mbps?	200 Mbit/s	832 Mbit/s	832 Mbit/s	832 Mbit/s
Interrupts	No	No	No	No	No	Optional	No	No	No
DRM support	No	No	No	No	Yes	N/A	Yes	Yes	Yes
encrypt user	No	No	No	No	Yes	No	No	No	No
Simplified specifications.	Yes	Yes	No	No	unknown	Yes	Yes	No	No
Membership cost	JEDEC: US$4,400/year, optional					SD Card Association: US$2000/year, general; US$4500/year, executive

How to choose a memory card?

It is worth highlighting a number of points that influence the choice of a memory card:

Memory card capacity

It is important to know that the actual amount of memory that the card has differs from the theoretical maximum that is written on the packaging. This is due to the fact that part of the card is occupied by service information: file data, service information, information to protect the memory card from failures, etc. On average, the actual amount of memory is 10% less than promised.

Speed

Speed ​​is fun. The faster the card, the less time it will take to write data to the card. A fast card will allow the camera to take more pictures in a short period of time. Super, Ultra, Pro, Xtream memory cards have higher speed compared to other cards. Per unit of speed is selected. The speed of the 133x card is twice as fast as the 66x card. The designation 1x means a speed of 150 KB per second.

Reliability

According to testing data, xD and Compact Flash cards are the most secure. Modern maps The memories are designed for several write-rewrite cycles, which ensures data safety for at least 5 years.

Protection

Many memory cards, such as SD, Memory Stick, have the ability to protect information from illegal use.

Memory card prices

Prices for memory cards vary accordingly depending on the parameters listed above and the “brand name”.

Brand

The choice of manufacturer (brand) of memory cards often plays a big role for customers. Fan sentiment is especially strong among young people and amateur photographers. There is a colossal number of opinions, tests, disputes about which memory card manufacturer is the best! According to the results of some tests, Kingston memory cards are the fastest; according to the results of others, Transcend cards. Some consider Microdia the most reliable brand, others Sandisk. As in the case of mobile phones, there is no clear opinion on this matter.

Types of memory cards

Compact Flash (CF)- one of the oldest and most common types of memory cards. The format was developed by SanDisk Corporation in 1994. Most digital cameras, PDAs, MP3 players and other devices support Compact Flash cards. The Compact Flash CF memory card is ideal for photography enthusiasts. In fact, no card can boast such speeds and capacities as the Compact Flash card. Today Compact Flash cards have capacities from 2 MB to 128 GB. The most popular “size” of Compact Flash is 16Gb and 32Gb. In terms of speed, Compact Flash 600x and Compact Flash 667x are currently the fastest cards in the series. But it is not only the speed of Compact Flash that has become the key to its popularity. Compact Flash type has one of the most optimal volume/price ratios.

As technology developed, this format evolved. CompactFlash Type II (CF Type II) Characterized by increased read/write speed and slightly larger thickness. Digital equipment with a CompactFlash Type II connector also supports a Compact Flash card.

The most well-known manufacturers of Compact Flash CF are A-DATA, ATP, Canon, FujiFilm, Kingston Technology, Kodak, Lexar, Memorex, Olympus, Panasonic, PNY, Ritek, SanDisk, Samsung, Sony, Toshiba, Transcend, Verbatim Corporation, UMAX.

Microdrive — This is not exactly a memory card, but rather a miniature one HDD. Compactflash Microdrive has a similar housing and connection connector Compact Flash II. However, the disadvantages of the CF Microdrive, such as increased power consumption and heat dissipation, low performance, and sensitivity to vibrations, are slowly pushing it out of the market. On the plus side, the Microdrive card has a fairly low price in relation to its volume. The compactflash Microdrive capacity ranges between 170 MB and 8 GB. The Microdrive card is integrated into some devices: Apple iPod mini - 4GB and 6GB Hitachi Microdrive, HTC Athena 8GB Hitachi Microdrive, iriver H10 - 5GB and 6GB Seagate Microdrive, etc. The CF Microdrive file system is NTFS.

Secure Digital (SD) is a joint development of Panasonic, Toshiba and SanDisk. At the moment, Secure Digital card is another one of the most common data storage formats. The advantages of the Secure Digital card are its small sizes, high write and read speeds, low power consumption, the ability to protect information stored on it from copying, accidental erasure or destruction, and mechanical strength. The standard file system for Secure Digital SD cards is FAT32. The maximum speed of the Secure Digital card is 300x (that is, 45000 kB/s). Secure Digital memory does not exceed 4 GB.

Expanding the capabilities of the Secure Digital card has led to the emergence of additional formats - Secure Digital HC (SDHC) with a maximum volume of 32GB and Secure Digital XC (SDXC) with a capacity of up to 2TB.

Formats have been developed for miniature equipment MiniSD(21.5x20x1.4 mm), MicroSD(11x15x1 mm) and MicroSDHC(11x15x1 mm), which have adapters (adapters) with which they can be inserted into any slot for a regular SD card. Cards of this size are usually used in cell phones, since their compactness makes it possible not to increase the size and weight of modern devices.

MiniSDHC(Mini Secure Digital High Capacity) - is an extension of the miniSD format and allows the production of memory cards with a capacity of 4 GB or more. However, they are only compatible with devices that support MiniSDHC.

xD-Picture— developed in 2001 by well-known manufacturers of digital photographic equipment, Olympus and Fuji. The advantages of the xD-Picture card include its compactness, reliability, speed, and low power consumption. Disadvantages: Together with Sony Memory Stick, this is one of the most expensive memory cards. The xD memory card is found only in Olympus and Fuji digital cameras. In addition, the xD Picture memory is suitable for storing digital films. Compatibility: xD -> Compact Flash (with adapter).

There is an external adapter that allows xD-Picture cards to be used in the SmartMedia slot, but it does not fit completely into the SM slot. There is a limitation on the size of the xD card used (128, sometimes 256 MB), and there may also be limitations in the operation of the reader.

SmartMedia is a portable flash memory card created by Toshiba, Olympus and Fuji. At the moment, SmartMedia card has almost completely disappeared from circulation. It is very rare to find only Japanese digital cameras (for example, Olympus) from previous years with support for Smart Media. But Olympus limits the functionality of non-native cards, and purchasing them will cost significantly more. The advantages of the card include low price and compactness. The disadvantages are the small amount of built-in memory (128 MB SmartMedia cards are the limit), the lack of a memory controller to reduce the price, mechanical insecurity and short service life (no more than 5 years). The SmartMedia memory card exists in two versions - 5 V and 3.3 V, they differ only in the position of the cut corner.

Memory Stick— Unique cards based on flash memory technology, developed by the world famous company Sony exclusively for its products. This is why Sony Memory Sticks are the most expensive cards on the market, sharing first place with xD. Sony Memory Stick is not just one, but a whole family of memory cards. It also includes Memory Stick Pro, a faster option, and Memory Stick Duo, a more compact and expensive card. Memory Stick Pro Duo is used in camcorders, digital cameras, personal computers, printers, game consoles PSP and some mobile phones Sony Ericsson.

The capacity of the Memory Stick never exceeded 128 MB, as Memory Stick Duo(also no more than 128MB). More advanced in this matter Memory Stick PRO(1GB) and Memory Stick PRO Duo (8-16GB). They all differ in size, however, there are special adapters for connecting modules of one type to a slot of another type.

Cards Memory Stick Pro-HG Duo were announced at the end of 2006. This is a high speed version of Memory stick PRO for use in HDTV cameras. And a little later - in 2008 - the Memory Stick PRO Duo Mark 2 card was released, the volume of which was 16 GB.

Micro Memory Stick- has a very small size (15 x 12.5 x 1.2 mm). Designed for use in Sony Ericsson mobile phones. The advantage of microMMC (besides its size) is that the information on it is protected from unauthorized copying.

MultiMediaCard (MMC)- became the first memory card designed specifically for use in mobile phones and players. MMC appeared in 1997 thanks to the efforts of Sandisk and Siemens. The first MMC memory cards were actively promoted by mobile phone manufacturers Nokia phones and Siemens. The advantages of the MultiMedia Card are its small size, as well as its robust mechanical design and low power consumption. Among the disadvantages of the Multi Media Card are the slow interface and fairly high cost. The MMC multimedia card is mostly compatible with the later developed SD card and can be used instead of SD.

The development of secure digital MultiMedia card led to the creation Reduced Size - Multi Media Card (RS-MMC)). The RS-MMC memory card is half the size of a standard MMC card and weighs only 1g. An adapter is required to ensure compatibility with the existing MMC standard when using RS-MMC cards. In terms of speed, they are similar to MMC cards, the maximum capacity of which today is 2 GB. RS-MMC is found in some Nokia and Siemens models.

There is also a modification of these cards called DV-RS-MMC, this card consumes less energy, as a result the phone will have to be charged less often. It is also worth noting that some Nokia smartphone models only support DV-RS-MMC cards. Compatibility: RS-MMC\DV-RS-MMC -> MMC -> SD (with adapter).

Memory cards MMCPlus appeared in 2005, their main difference from SD and MMC cards is their high data transfer speed (up to 52 Mb/s). Map MMCPlus HC(High Capacity) is an extension of MMCPlus. The capacity of this model is 4GB. Distinctive feature MMCPlus HC is that it can only be used with compatible devices. And in devices without support it works like a standard MMC.

microMMC— designed for mobile devices with ECC support. (Error Checking and Correction - detecting and correcting errors when writing/reading). The advantage is low power consumption, due to which the cell phone will not drain so quickly.

MiCard (Multiple Interface card) is a multi-interface card developed by the Taiwan Industrial Technology Research Institute, compatible with existing USB ports, as well as connectors for MMC cards. This is a new type of card, the advantage of which is high data transfer speed (480 Mbit/s). MiCard is used to directly transfer data between a portable device and a desktop computer without connecting a card reader.

Multimedia Card (MMC) is a portable flash memory card used in digital cameras, mobile phones, etc.

Cards of the MultiMedia Card type were developed in 1997 by SanDisk and Siemens based on Toshiba NAND memory, have a seven-pin connector (designed to minimize the risk of damage to the contacts), the card consists of a plastic shell and a printed circuit board on which the memory chip is located, microcontroller and contacts. Despite the serial nature of the MMC, data and commands can be transmitted simultaneously. MultiMedia Card operates with a voltage of 2.0V-3.6V, however, there are also options with reduced power requirements. SD Card has a nine-pin interface, developed jointly by Matsushita, SanDisk and Toshiba in 2000.

There is also a Micro Memory Card (MMC), which is structurally identical to the Multimedia Card, but differs in logical layout and is intended exclusively for use in SIMATIC S7 programmable logic controllers from Siemens AG.

Size 24x32x1.5 mm.

Since 2004, also produced in a smaller case 24x18x1.5 mm

end of form beginning of form With a simple mechanical adapter, RS-MMC cards can be used with equipment designed for “full-size” MMCs. Dual Voltage Reduced Size MMC (MMCmobile) are also available, which can operate not only on the standard 3 V supply voltage, but also on 1.8 V.

MMC is mostly compatible with the later developed SD card and can be used instead of SD. In the opposite direction, replacement is most often impossible, since SD cards are thicker than MMC and simply mechanically may not fit into the MMC card slot.

MMC uses a relatively simple open data transfer protocol, therefore, unlike Secure Digital (SD), it can be used in homemade devices.