What is SD MMC. MMC.

Introducing from traceable tendencies among memory cards, in addition to itself, of course, their further miniaturization is their further miniaturization, in the light of which the prospects of the most popular compactflash carriers seem increasingly foggy. In this article we will try to evaluate the performance of two MMC and SD memory cards of one of the largest manufacturers of Pretec Corporation. But not only they will become the object of our attention. In such a fine case, as a clarification of the actual speed of memory cards, very significant attention to the final results always have devices that read information from them. Unfortunately, the speed of reading and writing compact media we have to determine indirectly, and not directly. The card reader becomes "external" in the chain, which has its own characteristics. It is he who in most cases is the reason that we cannot achieve the speed of memory cards declared by manufacturers. For this reason, we have a particular interest to the new PRETEC card reader, which we decided to compare in efficiency with the device of SanDisk, we used earlier. In order for the picture here more objective, we decided to produce and re-measure the speed of the memory card previously tested TURBO SD A-DATA companywhich then showed not so high results that could be calculated on the basis of the claimed characteristics.

Pretec E-Disk II USB Card Reader

Start the view of the participants this time we decided with the new card reader E-Disk II. At first glance it may seem that you are dealing with a regular USB flash drive, so this miniature drive is similar to this category of devices in appearance and sizes. However, with closest communication it becomes clear that it is not. In the "streamlined" case from translucent blue plastic under the folding lid there is a compartment to install the memory cards of two categories.

Under the removable cap, which however continues to remain hanging on a thin metal chain, a USB connector is detected. At the end of the chain there is an oval metal plastic with the name of the manufacturer and a miniature "carabiner", thanks to which you can use a card reader as an ordinary keychain. Finishing the description of this memory card reader, you can mention the presence of a LED indicator of the operation mode.

Among the technical characteristics that are not mentioned by us, it is necessary to note the support of the USB 2.0 interface. Naturally, this stylish card reader can be used not only for its direct purpose to read the SD and MMC memory cards, but also as a regular USB flash drive. To do this, it is only necessary to leave one of the above-mentioned media in it. :)

The estimated retail cost of card reader is equal to 11 cu

Pretec MMC Plus 1 GB

The MMC Plus family memory card, which fell to us, did not have an inscription on it 266x, denoting the transfer speed, which would allow it to completely identify with the carrier presented on the manufacturer's website. There are no mention of speed characteristics and on the package. In such a situation, the testing we spend is particularly relevant and will contribute to the establishment of truth.
The estimated retail cost of a 2 GB memory card is 150 cu.

Pretec SD 133x 2 GB

The SECURE DIGITAL card family includes carriers of 256 MB to 4 MB. The declared transfer rate of 133x indicates the reacing of the turn of 20 MB / s. Memory cards are made based on SLC NAND technology (65 nm).
The estimated retail cost of a 2 GB memory card is 170 cu.

Testing technique

List of programs used for testing:

FC-Test version 1.0;
AIDA version 3.95.

During operation, a test platform of the following configuration was used:

Motherboard - Albatron PX865PE PRO;
Central processor - Intel Pentium 4 2.4 GHz;
Hard disk - IBM DTLA-307015 15 GB;
Graphic adapter - Radeon 7000 32 MB;
RAM - 256 MB;
Operating system - Microsoft Windows 2000 with Service Pack 4.

Media testing occurred using SanDisk ImageMate 5-in-1 Reader / Writer and Pretec E-Disk II Card Reader.

FC-TEST.

During the test using the FC-TEST program, the real characteristics of the speed of memory cards, and, in this case, through their results and the effectiveness of the card reader you are interested in. With this utility, situations related to the use of three patterns reflecting the effect of dimensions (1, 10 and 100 MB) and the number of files (1, 10 and 100) to the speed of carriers are reproduced.

First, let's see how media behave when using a pattern consisting of a hundred files one megabyte.

The first diagram presents the results of measuring the recording speed (creation) of files. In the case of using the SDISK card reader, the pretec SD carrier is in the first place, a slightly ahead of his opponent in the face of the A-Data card. We will not carry out a direct comparison between medium-type media, but we note that the PRETEC MMC Plus card at the recording speed is very behind the other two test participants.
The use of the PRETEC card reader E-DISK II leads to a wonderful reincarnation of the accuracy of not very fast devices. All media demonstrate sharply increased recording speed. This is especially clearly seen this on the example of the MMC Plus card, the speed of which increases almost six times, allowing it to climb to the very top of the chart. Very noticeable speed gains and in two other SD media. To a greater extent, this concerns the PRETEC product.

A diagram with the results of measuring the speed of reading a hundred files by one megabyte, in the case of using SANDISK card reader, indicates that according to this indicator, both SD carriers show almost the same speed, but the product Pretec is a little bit ahead. Noticeably lags behind them at the speed of reading MMC memory card.
The use of PRETEC card reader for testing media allows you to get more than a noticeable speed gain in all three participants. This is especially impressive it looks like a MMC memory card. Her read speed rose six times. A good "purchase" was obtained from SD carriers, newly demonstrated almost the same results with a slight advantage of PRETEC card. The speed of reading from both SD carriers has grown almost twice.

We now turn to the consideration of the situation associated with the use of a pattern consisting of ten files for ten megabytes.

The graph results reflecting the speed of recording media using SanDisk card reader, we see that the PRETEC SD memory card is a bit ahead of the A-DATA product. MMC media demonstrates a very modest result.
In the case of using the PRETEC card reader's working device, all media reopened the "second breathing". The MMC memory card is stronger than all. She has an almost six-time growth rate of recording. Pretec SD carrier increases its speed by almost twice, and it is noticeably ahead of his opponent in the face of the A-Data Turbo SD card.

On the next diagram, we see that reading files from media in the Sandisk card reader leads to the fact that both SD memory cards have full equality of results. The MMC medium still shows a stable low recording speed.
The use of PRETEC's new card reader files to read once again led to a very significant increase in performance indicators of all three media. SD card reading speed is equal to each other and about two times more than when using SANDISK card reader. MMC media speed rose by about six times.

It's time to take a look at the speed of the media shown in the case of working with a pattern consisting of one large file of 100 MB.

On the chart at the speed of the memory card on the memory card, the results obtained using the SANDISK card reader say that the Pretec SD carrier slightly overtakes his opponent. The MMC memory card is very low.
Replacing the card reader on the Pretec device leads to a tangible increase in the recording speed in all media. This is especially pronounced by the MMC memory card. Its speed has increased by about six times. Among the SD cards, the card reader was stronger than just all the replacement of the PRETEC product, whose recording speed increased by about two times, and it began to noticeably overtake the carrier of a similar type, produced by A-DATA.

The graph with the results obtained during the measurement of the reading speed of the devices can be seen that in the case of the SANDISK card reader, there is a complete parity to speed between the SD cards and a very noticeable lag on this MMC media indicator.
Once again, we also see the beneficial impact of the work of the PRETEC card reader at the speed of reading all three media we tested. The speed of the SD memory cards increased by about twice, and the MMC media is about six times.

Aida32.

The second stage of our testing is associated with measuring the performance of media using the AIDA32 program. During synthetic tests, we filmed linear reading and recording graphs, as well as access time. Based on the average indicators of the three of these parameters, appropriate charts were built.

Pretec MMC Plus: SanDisk ImageMate 5-in-1

Linear Write Speed.



Linear Read Speed.



Average Access Time.

Pretec MMC Plus: Pretec E-Disk II

Linear Write Speed.



Linear Read Speed.



Average Access Time.

Pretec SD 133x: SanDisk ImageMate 5-in-1

Linear Write Speed.



Linear Read Speed.



Average Access Time.

Pretec SD 133x: Pretec E-Disk II

Linear Write Speed.



Linear Read Speed.



Average Access Time.

A-DATA TURBO SD: Pretec E-Disk II

Linear Write Speed.



Linear Read Speed.



Average Access Time.

Let's start considering the results of synthetic tests from the indicators of the middle speed of the linear record.

The diagram is clearly seen that in the case of using SanDisk Card reader, both SD cards demonstrate identical speed. MMC medium speed is very far behind them.
Replacing the card reader to the new product of PRETEC leads to more than a semi-sightened increase in the average linear recording rate in both SD memory cards and approximately six-time MMC media.

The graph with the measurement results of the middle line of linear reading demonstrates in the case of the use of SANDISK card reader, the practical equality of the results in two SD memory cards and a noticeable lag from them MMC media.
The operation of memory cards through the PRETEC card reader gives a tangible, almost double, the increase in the average linear reading rate in the SD carriers that are almost equal to speed. The speed of the MMC card has greatly grown - in this case more than six times.

The measured average access time from the SD carriers in the case of using the SANDISK card reader turned out to be equal and non-disappointment. Some more it is at the MMC card.
It is curious that the application in the work of the PRETEC card reader led to a noticeable decrease in the average access time. This is especially noticeable at the MMC card. The SD media occurred to a lesser extent, but still a trifle, and nice.

Summarizing

In general, the main goal of this test was initially a memory card, but the results obtained in its course are forced first of all to talk about PRETEC E-DISK II card reader. Its work has become a vivid confirmation of the fact that the effective work of the fastest carriers will need an adequate reading and recording device. Our assumptions that during previous testing we did not always succeed in reaching the cards of the performance of the performance declared by manufacturers, it was precisely the fault of the Card Ruclear, in this case a vivid confirmation. Pretec's E-Disk II miniature device turned out to be "on the head" more efficiently than the similar card reader SanDisk ImageMate 5-in-1. It was especially strongly affected at the speed of reading and writing a MMC memory card, whose indicators immediately grew by about six times, reaching 9-10 MB / s. This was somewhat influenced by the SD carriers, where this growth reached a number of situations of approximately two-time magnitude. Due to this, they managed to reach the speed of reading 18 MB / s, which is already quite close to the indicators declared by manufacturers. Here you can also note that the PRETEC SD 133X memory card looked a bit more preferably a-Data Turbo SD, thanks to the greater recording speed.
Considering that manufacturers of flash memory carriers are constantly improving their characteristics, one can recommend all buyers of this product to pay close attention and card readers, since old models will not clearly be able to ensure the effective use of new memory cards. One of the first candidates for the acquisition is quite worthy to become Pretec E-Disk II. This compact device will not take a lot of space in your pocket and help the operation of memory cards in the most complete use of their speed characteristics. In addition, this device is capable of performing the functions of a regular USB flash drive, but it is worth the amount of money that will not cause shock from buyers.

Thanks to the company Norma Group for the memory card provided to test for testing and PRETEC card.

Multimediacard , officially abbreviated MMC. Is the memory card standard used for solid-state storage. The SanDisk and Siemens AG presented in 1997, the HCs are based on the surface contact with a low number of conclusions of the serial interface using a single block of a single memory stack, and, therefore, much less than in previous systems based on a high-pin parallel interfaces with using the traditional surface -mount assembly, such as CompactFlash. Both products were originally introduced using SanDisk NOR based on flash technology. MMC on the size of the postage stamp: 24 mm × 32 mm × 1.4 mm. MMC, initially used a 1-bit serial interface, but newer versions of the specification allow a 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 operates as a carrier of information for a portable device, in a form that can be easily deleted to access the computer. For example, a digital camera will use MMC to store image files. Through the MMC reader (as a rule, a small box that connects via a USB or any other serial connection, although some of them can be found integrated into the computer itself), the user can transmit pictures taken using a digital camera to its or its computer . Modern computers, like laptops and desktops, often have SD slots that can additionally read MMS if the operating system drivers can.

KMM are available in size up to 512 GB. They are used in almost all conditions in which memory cards are used as cell phones, digital audio players, digital cameras and PDAs. With the moment of the introduction of SD cards, several companies are building MMC slots to their devices (the exception is some mobile devices, such as Nokia 9300, the communicator in 2004, where the smaller MMS size is an advantage), but a little thinner, PIN-compatible KMm can be used practically Any device that can use SD cards if the software / firmware on the device is capable.

While some companies build MMC slots into the device, as in 2018 (SD cards are more common), the built-in MMC (EMMC) is still widely used in consumer electronics as the main tool for integrated storage in portable devices. It provides a flash memory system inexpensive with a built-in controller, which can be inside Android or Windows, telephone or in low-cost PC and may appear on the host as a boot device, instead of a more expensive form solid-state storage, for example, a traditional solid-state drive.

Open standard

The best of the four types of MMC cards (clockwise left right): MMC, RS-MMC, MMCPLUS, MMCMobile, Metal Expander

The bottom of four cards

This technology is the standard available for any company wishing to develop products based on it. There is no royalty free for devices that are accepted in MMC. Membership in the MMC Association should be purchased in order to make the cards themselves.

As of July 2009, Specifications version 4.4 (from March 2009) can be requested from MMCA, and after registering MMCA, you can download free. Older versions of the standard, as well as some additional standard enhancements, such as MICARD and SecureMC, must be purchased separately.

A very detailed version is available online, which contains the necessary information for writing the MMC driver.

As of September 23, 2008, the MMCA group has already turned all the specifications in the JEDEC of the Organization, including implemented MMC (electronic MMC) and MICARD assets. JEDEC is an organization engaged in standards for solid-state industry.

As of February 2015, the latest version of the Specification 5.1 may be requested from JEDEC, and after registering JEDEC, you can download free charge. Older versions of the standard, as well as some additional standard enhancements, such as MICARD and SecureMC, must be purchased separately.

Options

RS-MMC.

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

Modern continuation of RS-MMC is widely known as Minidrive. (MD-MMC.). MiniDrive is usually a microSD card adapter in RS-MMC forms factor. This allows the user to take advantage of the wider range of modern MMS available to exceed the historic 2 GB of limiting the old chip technology.

Version 4.x cards full-size and reduced card size can be sold as Mmcplus. and Mmcmobile. respectively.

Version 4.x cards are completely compatible with existing readers, but requires updated hardware / software to use your new features; Even if four-bit bus width and high-speed modes of operation are intentionally electrically compatible with SD, the initialization protocol is different, so firmware updates / software must use these functions in the SD reader.

MMCMICRO.

MMCMICRO. MMC micro size version. With dimensions 14 mm × 12 mm × 1.1 mm, even less and thinner than RS-MMC. As MMCMobile, MMCMICRO allows dual voltage, 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 tires features 4.x specifications, but not an eight-bit bus, due to lack of additional contacts.

Earlier she was known as S-card when Samsung was introduced on December 13, 2004. Later was adapted and implemented in 2005 by the Multimediacard Association (MMCA) as a third chart memory card in the Forms in Multimediacard Family.

MMCMICRO looks very similar to MicroSD, but these two formats are not physically compatible and have incompatible wiring.

Micard

Micard It is a back compatible expansion of the MMC standard with the theoretical maximum size of 2048 GB (2 TB) announced on June 2, 2007 The card consists of two detachable parts, just like microSD cards with an SD adapter. A small memory card is placed directly in the USB port, and also has MMC-compatible electrical contacts, which are included with the electromechanical seizure adapter in traditional MMC and SD card readers. To date, only one manufacturer (pretec) has released cards in this format.

Development of Taiwan, at the time of the announcement of the twelve Taiwanese companies (including ADATA Technology, Asustek, BenQ, Carry Computer Eng. Co., C-One Technology, Dbtel, Digital Card Co. and Richip Power) He signed a contract for the manufacture of a new memory card. Nevertheless, as of June 2011, no of the listed companies released any such cards, and no further statements were made of format plans.

The map was announced available, starting at the third quarter of 2007, he had to save 12 Taiwanese companies, which are planned to make a product and appropriate hardware to US $ 40 million in licensed fees, which allegedly will be paid to the owners of competing Flash formats - memory. The source card was supposed to have a capacity of 8 GB, while the standard would allow dimensions up to 2048 GB. It was announced to have a data transfer rate of 480 Mbps (60 MB / s), with plans to increase bandwidth over time.

SecureMMC.

Additional, optional, part of the MMC 4.x specification is the mechanism DRM is designed to compete with SD or Memory Stick memory card in this area. Very little information is known about how Securemc works or as its DRM characteristics compare it with competitors.

EMMC.

EMMC (built-in MMC), the architecture puts the MMC component (flash memory plus controller) in a small array of the mesh of the ball packet (BGA) IC for use in printed circuit boards as a built-in non-volatile memory system. EMMC exists in 100, 153, 169 ballpoints and is based on a parallel 8-bit interface. This is noticeably different from other MMC versions, as this is not a user of a removable card, but rather a constant mount to the circuit board. In case of a question arising from any memory or controller, the entire PCB (Printed Circuit Board) will need to be replaced.

EMMC does not support protocol SPI bus.

Almost all mobile phones and tablets used this shape for basic storage until 2016, in 2016, UFS began to take control over the market. The latest version of the EMMC standard (JESD84-B51) by JEDEC is version 5.1 released in February 2015 with a speed of competing discrete SATA-on solid-state disks (400 MB / s).

others

Seagate, Hitachi and others are in the process of release 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 expanded to allow the host controller to issue ATA commands to control the hard disk.

Table

A 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 (rarely)	1.4 mm	1 mm
1- bit SPI tire mode	Optional	Optional	Optional	Optional	yes	yes	yes	yes	yes
sPI Max Tire Frequency	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
4-bit MMC / SD Tire Mode	not	not	yes	yes	not	Optional	yes	yes	yes
8-bit MMC Tire Mode	not	not	yes	yes	not	not	not	not	not
DDR mode	not	not	yes	yes	unknown	unknown	unknown	unknown	unknown
Max MMC / SD Tire Frequency	20 MHz	20 MHz	52 MHz	52 MHz	20 MHz?	50 MHz	208 MHz	208 MHz	208 MHz
Max MMC / SD Data Rate	20 Mbps	20 Mbps	832 Mbps	832 Mbps	20 Mbps?	200 Mbps	832 Mbps	832 Mbps	832 Mbps
Interrupts	not	not	not	not	not	Optional	not	not	not
DRM Support	not	not	not	not	yes	N / A.	yes	yes	yes
encrypt the user	not	not	not	not	yes	not	not	not	not
Simplified specification.	yes	yes	not	not	unknown	yes	yes	not	not
Cost of membership	JEDEC: US \u200b\u200b$ 4,400 / year, at will					SD Card Association: US $ 2000 / Year, Common; US $ 4500 / year, executive

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

Multimedia Card cards were developed in 1997 by SanDisk and Siemens based on Toshiba Nand-memory, have a seven-contact 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 microcircuit is located, Microcontroller and contacts. Despite the sequential nature of MMC, data and commands can be transmitted simultaneously. Multimedia Card works with voltage 2.0V-3.6V, but there are also options with reduced nutritional requirements. SD Card has a nine-contact interface, developed jointly Matsushita, SanDisk and Toshiba in 2000

There is also a Micro Memory Card (MMC), constructively identical Multimedia Card card, but differing in logical markup and intended solely for use in programmable logical controllers SIMATIC S7 Siemens AG.

Size 24 × 32 × 1.5 mm.

Since 2004, there are also 24 × 18 × 1.5 mm in the reduced housing

you can use an endormormal form for a simple mechanical RS-MMC card adapter using equipment designed for "full-size" MMC. Dual Voltage Reduced Size MMC (MMCMOBILE) is also available, which can not work not only on the standard supply voltage of 3 V, but also by 1.8 V.

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

MMC uses a relatively simple public data transmission protocol, therefore, in contrast to Secure Digital (SD), can be used in homemade devices.

As can be seen from the picture after the transmission of the command frame, it is necessary to continue reading bytes (NCR) from MicroSD before receiving an answer (R1), while the CS level must be active "0".

Depending on the command index, the answer may not only be R1 (see the main command set) on the CMD58 answer R3 (R1 and the final 32-bit value of OCR), and some commands need more time NCR and they will answer R1b.. This is the answer R1, followed by the employment flag (the signal on the "DO" line is held by a low-level card while the internal process continues). The host controller should wait for the end of the process until "DO" does not switch to a high level state (i.e. wait for 0xFF). As well as R2 when requesting status status Status.

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

Answer R1 with 0x00 valuemeans the successful completion of the command, otherwise the corresponding flag will be installed.

Response structure R1.

R2 response structure.

Initialization in SPI mode.

After resetting and pumping the power, the MMC Map is installed in the MMC (Serial Peripheral Interface) mode, to transfer to the SPI mode, you must do the following:

1. After reaching nutrition 2.2 V, wait at least milliseconds, set a high level on the DI and CS lines and give about 80 pulses to the CLK output. After such a procedure, the card will be ready to accept the native command.
2. Send the CMD0 command (software reset). The card must respond (R1) with a set of waiting bits (0x01).
3. Send the CMD1 command (to start card initialization). Wait for the 0x00 response to confirm the completion of the processinitialization.

Let me remind you that the CMD0 command must contain the CRC correct field. It makes no sense to count on, since there are no arguments in this team, it constantly has a value of 0x95. When the card enters the SPI mode, the CRC function will be disabled and will not be checked. The CRC option can be turned on with the CMD59 command.

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 formed by transmitting by SPI value 0xFF10 times in a row When set high levels on the linesDi and cs.

After idle more than 5 ms, the memory card goes into an energy-saving mode, and can only accept CMD0, CMD1 and CMD58 commands. For this, the initialization process (CMD1) must be repeated almost every time when reading / writing a data block or check the status of the map.

For SDC cards in case of deviation of the commandCMD1 It is recommended to use the ACMD41 command.

The initialization process itself may take relatively long time (depending on the volume of the map) and can reach hundreds of milliseconds.

Reading and writing a block of data.

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

Waiting for the addressing error when performing read / write commands, it is necessary that the address indicated clearly starts the sector. To do this, you can reset the bit "0" 3 byte of the address of the sector, i.e. Do it even, and the younger should always have a value of 0x00.

Reading data block.

The data block read algorithm is as follows:

• After confirmation of the initialization, we transmit the CMD17 command (answer R1), with the address of the required sector.
• We transmit 0xFF to receiving the start byte 0xfe.
• We accept the data block (by suturing 512 bytes) and 2 CRC bytes.

The CRC value is not necessary, but the adoption procedure (transmission of 0xFF from the MC) is necessary.

Reading block.

Record data block.

The data block record algorithm is as follows:

• If a simple card has been more than 5 ms by sending a CMD1 command (response R1).
• After confirmation of the initialization, we transmit the CMD24 command (answer R1), with the address of the required sector.
• We transmit the start byte 0xfe.
• We transmit the data block (on suturing 512 bytes) and 2 CRC bytes.
• We get byte confirmation recording.
• We are waiting for the end of the record (byte changes 0x00).

The data block may be less than 512 bytes when the block length changes the CMD16 command.

The CRC value is not necessary, but the transfer procedure by any values \u200b\u200bis necessary.

Downtime estimate can be programmatically and not to do, and immediately give the initialization command. The software implementation faced an incorrect entry, for some reason all the bytes were recorded in the Sector with the shift to the left. The problem was solved only by passing the start bit (0xF) twice.

Record block.

Confirmation byte when writing a data block.

Recording / reading multiple blocks in a row.

Using commands CMD18., CMD25 You can read / write several blocks in a row or the so-called multilox read / write. If the number of blocks has not been specified, the read / write process can be stopped by the CMD12 commands when reading, as well as the transmission of the marker " Stop Tran"When recording, respectively.

Practical use.

The practical application of memory cards is quite wide. In the last of its design, MicroSD involved to write indications from various sensors (temperature, alarm) during the day every hour. The data is stored as follows:

• The year is taken by the last two digits - it corresponds to the first (main) byte address of the memory card sector.
• Month, two digits - this corresponds to the second, senior byte address of the memory card sector.
• Day, two digits are multiplied by 2 (in order to avoid outside the border of the sector) - this is the third, middle byte address of the memory card sector.
• Junior, the fourth byte always "0".

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

Who needs to throw the code fragment on the assembler for 18 peaks.

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