Despite the progress of computer technology, just 3-4 years ago many new computers (and even more so older ones) included a floppy drive. Significant reductions in the cost of optical drives and CDs have not been able to replace 3.5-inch floppy disks. It's inconvenient to use optical media and that's it. While reading data from them does not cause any particular discomfort, writing and deleting them already required some time. And the reliability of disks, although many times higher than that of floppy disks, still begins to decline after some time, especially after active use. As always, at the most inopportune moment, the drive will “kick” due to old age (its own or the disk) and say that the disk is not noticeable on the horizon.

That's why floppy disks lasted so long. It is still quite possible to carry small things like documents or source codes of programs on them. But now, even for this type of data, sometimes 1.38 MB of free space is not enough.

The solution to the problem has been looming for quite some time. Its name is flash memory. It was invented back in the 80s of the last century, but reached actual mass products by the end of the 90s. And at first it was available to us as memory cards, and then in the form of MP3 players, which today have already changed the abbreviation MP3 to a prouder and more general epithet “digital”.

This was followed by the advent of USB flash drives. The process of their penetration was not the fastest at first. It began with the appearance of 16-64 MB solutions. Now this is minuscule, but 8 years ago, compared to a floppy disk, it was wow. And added to this was ease of use, high read/write speed and, of course, a high price. At that time, such flash drives were more expensive than an optical drive, which themselves were valued at about $100.

However, the convenience of flash drives has had a decisive influence on consumer choice. As a result, a real boom began in 2005. The cost of flash memory has fallen many times, and along with it the capacity of storage devices has increased. As a result, today you can buy a 32 GB flash drive for just 2000-2500 rubles, whereas a year ago it cost almost twice as much.

Progress in the field of flash memory has been so successful that today it is already beginning to compete with hard drives. So far only in the area of ​​read/write speed and access time, as well as in energy performance and durability, but victory in capacity in the coming years also cannot be ruled out. The only advantage of HDD is the price. One “hard” gigabyte costs much less. But this is only a matter of time.

So, flash memory is one of the most promising computer technologies for storing data. But where did it come from and what are its possible limitations and disadvantages? It is precisely these questions that this article aims to answer.

Past

While Japanese shippers were unloading one of the first shipments of Apple computers, which arrived in refrigerators because of the apple on the boxes, a Japanese scientist named Fujio Masuoki was working on a new type of memory in the Toshiba research laboratory. They didn’t come up with a name for it right away, but the scientist saw the prospects for the invention from the very beginning.

However, the name was decided on quite quickly. Fujio's colleague, Mr. Shoji Ariizumi, suggested calling the new memory "flash". One translation of this word means a camera flash (and, in principle, any other flash of light). This idea was suggested to Shoji by the method of erasing data.

The new technology was presented in 1984 in San Francisco at an event called the International Electron Devices Meeting, held by the IEEE. It was noticed immediately by quite large companies. For example, Intel released its first commercial NOR chip in 1988.

Five years later, in 1989, Toshiba introduced NAND flash memory technology at a similar event. Today this type is used in the vast majority of devices. We'll tell you why exactly in the next section.

NOR and NAND

NOR memory was introduced a little earlier because it is a little easier to manufacture, and its transistors in their structure resemble a regular MOSFET transistor (channel unipolar field-effect transistor). The only difference is that in NOR memory the transistor, in addition to the control gate, has a second, “floating” gate. The latter, with the help of a special insulating layer, can retain electrons for many years, keeping the transistor not discharged.

In general, NOR memory got its name because it works as a NOR gate (NOR is a logical NOR operation; it takes the value “true” only when both inputs are “false”). So the empty NOR memory cell is filled with the logic value "1". By the way, the same applies to NAND memory. And, as you might guess, it got its name because of a similar principle of operation with a NAND gate (NAND is a logical NAND operation; it takes the value “false” only when “true” is applied to both inputs).

What do these same “NOT-AND” and “NOT-OR” result in in practice? The fact is that the NOR memory chip can only be cleared entirely. Although in more modern incarnations of this technology, the chip is divided into several blocks, usually occupying 64, 128 or 256 KB. But this type of memory has an external address bus, which allows byte-by-byte reading and programming (writing). This allows you not only to access data directly as accurately as possible, but also to execute it directly “on the spot”, without unloading all the information into RAM. This capability is called XIP (eXecute In Place).

It's also worth talking about a relatively new NOR memory function called BBM (Bad Block Management). Over time, some of the cells may become unusable (more precisely, their recording will become unavailable) and the chip controller, noticing this, will reassign the address of such cells to another, still working block. Hard drives do something similar, as we wrote about in the article "".

Thus, NOR memory is well suited for cases where maximum accuracy of data reading and fairly infrequent changes are required. Can you guess where we're going with this? That's right - to the firmware of various devices, in particular the BIOS of motherboards, video cards, etc. This is where NOR flash is now most often used.

As for NAND, the situation with it is a little more tricky. Reading data can only be done page by page, and writing can only be done block by block. One block consists of several pages, and one page is usually 512, 2048, or 4096 bytes in size. The number of pages in a block usually varies from 32 to 128. So there is no question of any “on-site” execution. Another limitation of NAND memory is that a block can only be written sequentially.

As a result, such precision (although it would be more correct to say “not precision”) sometimes leads to errors, especially if you have to deal with MLC memory (more on this type below). To correct them, the ECC mechanism is used. It can correct 1 to 22 bits in every 2048 bits of data. If correction is not possible, the mechanism detects that there was an error while writing or erasing data and the block is marked as "bad".

By the way, to prevent the formation of bad blocks in flash memory, there is a special method called “wear levelling” (literally “wear level”). It works quite simply. Since the "survivability" of a flash memory block depends on the number of erase and write operations, and this number is different for different blocks, the device controller counts the number of these operations for blocks, trying to write to those that have been used less over time. That is, those that are less “worn out”.

Well, as for the scope of application of NAND memory, due to the possibility of denser placement of transistors, and at the same time cheaper production, it is used in all flash memory cards and USB flash drives, as well as SSDs.

Well, a little about SLC (Single-Level Cell - single-level cell) and MLC (Multi-Level Cell - multi-level cell) cells. Initially, only the first type was available. It assumes that only two states, that is, one bit of data, can be stored in one cell. MLC chips were invented later. Their capabilities are a little wider - depending on the voltage, the controller can read more than two values ​​from them (usually four), which allows you to store 2 or more bits in one cell.

The advantages of MLC are obvious - with the same physical size, twice as much data fits into one cell. The disadvantages, however, are no less significant. First of all, this is the reading speed - it is naturally lower than that of SLC. After all, it is necessary to create a more accurate voltage, and after that it is necessary to correctly decipher the information received. And then the second drawback arises - inevitable errors when reading and writing data. No, the data is not damaged, but it does affect the speed of operation.

A rather significant drawback of flash memory is the limited number of data write and erase cycles. In this regard, it still can’t compete very well with hard drives, but overall the situation is improving every year. Here are the service life data for different types of flash memory:

• SLC NAND – up to 100 thousand cycles;
• MLC NAND – up to 10 thousand cycles;
• SLC NOR – from 100 to 1000 thousand cycles;
• MLC NOR – up to 100 thousand cycles.

Here's another disadvantage of MLC memory - it is less durable. Well, NOR flash is generally beyond competition. True, this is of little use to the average person - anyway, his flash drive is most likely built on the basis of NAND flash, and even on MLC chips. However, technology does not stand still and NAND flash with millions of cycles of writing and erasing data is gradually coming to the masses. So over time, these parameters will become of little significance to us.

"Cards"

Having dealt with the types of flash memory, let's now move on to real products based on it. Of course, we will omit the description of BIOS chips, since most readers are of little interest to them. Just like it makes no sense to talk about USB flash drives. With them, everything is extremely simple: they are connected via a USB interface, the chips installed inside are entirely dependent on the manufacturer. There are no standards for these media, except for the need for USB compatibility.

But standards are required for flash cards, which are used today in digital cameras, players, mobile phones and other mobile devices. A card reader for them is available in most laptops and netbooks, and one can also be found in household DVD (or Blu-ray) players or car radios.

There is one universal characteristic for these devices - the number of supported memory cards. Sometimes on card readers you can see proud inscriptions “20-in-1” or even “30-in-1”, indicating the number of supported formats. But what is most surprising is that there are only 6 fundamentally different mass formats. All the rest are their modifications. It is these six standards that we will focus on further.

CompactFlash

The CompactFlash format occupies a special place among all other flash memory card formats. First of all, because it was the very first mass standard. It was introduced by SanDisk in 1994. And it is still actively used in digital SLR cameras, as well as computer routers and other highly specialized devices.

The most interesting thing is that the first CF cards were based on NOR chips manufactured by Intel. But then they were quickly transferred to NAND flash, which reduced the cost and increased capacity.

CompactFlash was created as a format for external data storage. But since there were no card readers 15 years ago, and USB was just being designed, CF cards were created based on the ATA (IDE) interface specifications. Thus, such a card can be connected to a regular IDE connector or inserted into a PC Card slot via a passive adapter. This is why CompactFlash is very convenient to use in routers and similar devices - speed and large volume are not required there, but size, shock resistance and low heating are much more relevant.

In addition, it is not difficult to make an adapter for a USB or FireWire interface. And, most interestingly, most card readers use the CompactFlash I/O system to exchange data between the computer and other formats: SD/MMC, Memoty Stick, xD and SmartMedia.

Now about the various modifications of the CompactFlash standard. Initially, such cards were issued in a single “cartridge” measuring 43x36x3.3 mm. It is still used today. But when the one-inch IBM Microdrive hard drive was introduced, a second form factor with dimensions of 43x36x5.0 mm was added. Thus, the first became known as CF Type I, and the second - CF Type II. After the release of the Microdrive (and its analogues) was stopped, the relevance of the CF Type II came to naught.

CompactFlash has several more revisions. Their need arose as read/write speeds and volumes increased. So revision 2.0 increased the maximum speed to 16 MB/s. Later, revision 3.0 appeared, increasing this value to 66 MB/s. Well, the latest version 4.0/4.1 allows you to exchange data at speeds of up to 133 MB/s. The last value corresponds to the UDMA133 standard, which is also losing its relevance.

To replace the fourth revision, they are already preparing... no, not a new revision - a new format - CFast. Its main fundamental difference is the use of the SerialATA interface instead of IDE. Of course, this completely covers backward compatibility with the previous type of connector, but it increases the maximum speed to 300 MB/s and the ability to expand the volume to much more than 137 GB. Note that CFast uses seven pins for data exchange, just like a regular SATA interface. But power is supplied through 17 pins, whereas SATA devices have 15. So you won’t be able to directly connect the CFast card to the motherboard; you’ll have to use an adapter. Such cards should appear this year. In January, at CES 2009, the first samples with a capacity of 32 GB were already demonstrated.

Now it remains to talk about the speed of data exchange and the volumes of CompactFlash cards available today. The speed of CF cards (and other flash memory drives, except SSDs too) is measured exactly the same as for CD drives. That is, 1x corresponds to 150 KB/s. The fastest representatives have the inscription 300x, which corresponds to 45 MB/s. In principle, it’s not small, but it’s far from hard drives paired with SSDs. But over time, the speed will only increase.

Well, as for the volume, CompactFlash cards with capacities ranging from 2 MB to 100 GB have been released over the years. Today, the most common options are from 1 to 32 GB. However, 48, 64 and 100 GB versions are already available for sale, although they are still quite rare. So far, the CompactFlash format offers the highest capacity flash memory cards. But others may offer other advantages. We read about them further.

SmartMedia

SmartMedia became the second mass format of flash cards. It was introduced a year later than CompactFlash - in the summer of 1995. Actually, it was created as a competitor to CF. What did SmartMedia have to offer? First of all, smaller sizes. And to be even more precise, only a smaller thickness - only 0.76 mm; the width and length of such cards was 45x37 mm, while for CompactFlash these parameters are almost the same - 43x36 mm. It should be noted that in terms of thickness, SM has not yet surpassed any other format. Even ultra-compact microSD cards are fatter - 1 mm.

This figure was achieved thanks to the removal of the controller chip. It was transferred to the card reader. Yes, and inside the SM card itself, at first there could be one NAND chip, but then, as technology improved, there were more of them.

But the absence of a controller inside the card has certain disadvantages. Firstly, as the volume grew and new media models were released, the card reader firmware had to be updated. And this operation was not always available if the card reader was very old. Also, over time, confusion began with the operating voltage of SmartMedia cards. Initially it was 5.0 V, and then 3.3 V. And if the card reader did not support one of them, then it could not work with such cards. Moreover, when inserting a 3.3 volt card into a 5.0 volt card reader, it could be damaged or burned.

Secondly, for the SmartMedia format it is impossible to use the method of calculating the wear level of flash memory blocks (we described the wear levelling method in the last section). And this potentially threatens to shorten the life of the memory card.

However, all this did not prevent SmartMedia from being used for quite a long time as the main format for digital cameras - in 2001, up to half of such devices on the market supported it, although at that time this market was much more modest than today. SmartMedia has not found itself in other digital devices such as players, PDAs or mobile phones. And camera manufacturers began to abandon SM. Cameras were becoming smaller and smaller and the thinness of these cards was no longer enough. Well, the second significant disadvantage is the growing need for more capacity. SmartMedia cards reached a capacity of only 128 MB. 256 MB variants were planned, but they were never released.

In general, SmartMedia was conceived as a replacement for 3.5-inch floppy disks. A special adapter called FlashPath was even released for them. It was introduced in May 1998 and a year later they sold a million units. It was developed by SmartDisk, which, by the way, produced similar adapters for MemoryStick and SD/MMC cards.

The most amazing thing is that FlashPath can work with any floppy drive with an excellent “HD” (High-Density) logo. In short, anyone who reads a 1.44 MB floppy disk is suitable. But there is one "but". There is no way to do without it. And here there are even two of them. First, a special driver is required to recognize the FlashPath adapter and the card inside it. And if it is not available for the required OS, then it is in the air. So it will no longer be possible to boot from such a floppy disk. The second “but” is the speed of work. It does not exceed that when working from a regular floppy disk. And if 1.44 MB could be copied or written in a little more than a minute, then 64 MB would take more than an hour.

Today the SmartMedia format can be called dead. Some card readers still support it (especially the geeky all-in-1 ones), but this compatibility is simply not relevant. Although, of course, this standard made a certain contribution to the development of flash technologies.

The MMC format was introduced third in 1997. It was developed by SanDisk and Siemens AG. The abbreviation MMC stands for MultiMediaCard, which immediately indicates the purpose of the standard - digital multimedia devices. This is where MMC is most often used.

In principle, MMC is very closely related to SD, especially their first versions. However, they diverged in their development and today the second is the most common. So we will talk about it in the next subsection.

MMC, unlike CompactFlash and SmartMedia, has a more compact size. In terms of length and width: 24x32 mm. The thickness of MMC cards is 1.4 mm, which is approximately twice that of SM. But this parameter is not as critical as the other two measurements.

Over the entire existence of MMC, as many as eight different modifications of its cards have been presented. The first (simply MMC) uses a one-bit serial interface for data transmission, and its controller operates at a frequency of up to 20 MHz. This means a maximum speed of no more than 20 Mbps (2.5 MB/s or approximately 17x). In principle, quite modest by modern standards, but 12 years ago this was enough.

In 2004, the RS-MMC form factor was introduced. The prefix RS means Reduced-Size or “reduced size”. Its dimensions are as follows: 24x18x1.4 mm. You can see that the height has almost halved. Otherwise it was exactly the same MMC memory card. But to install it in a card reader you need to use a mechanical adapter.

The DV-MMC format turned out to be quite short-lived (DV stands for Dual-Voltage - double voltage). Such cards could operate at a standard voltage of 3.3 V and at a reduced voltage of 1.8 V. This is necessary to save energy. There is a clear focus on mobile devices here. But DV-MMC cards were quickly phased out due to the advent of the MMC+ (or MMCplus) and MMCmobile formats.

MMC+ and MMCmobile differed quite significantly from the original MMC specification and represented its fourth version. However, this did not prevent them from maintaining full backward compatibility with older card readers and devices, but to use their new capabilities, a firmware update was required. And these possibilities were as follows. To the one-bit data exchange interface, 4- and 8-bit ones were added. The controller frequency could be from 26 to 52 MHz. All this raised the maximum speed to 416 Mbit/s (52 MB/s). Both of these formats supported operation with a voltage of 1.8 or 3.3 V. In size, they did not differ from MMC and RS-MMC, MMCplus and MMCmobile, respectively.

Later, the smallest MMC appeared - MMCmicro. The card dimensions were 14x12x1.1 mm. This format was based on MMC+ with some limitations. In particular, due to the lack of additional contacts (MMC has 7, MMC+ has 13), the data exchange interface did not support 8-bit data transfer.

There is also such an unusual format as miCard. It was introduced in the summer of 2007 with the goal of creating a universal card that can be inserted into both an SD/MMC card reader and a USB connector. The first cards were supposed to have a capacity of 8 GB. The maximum reaches 2048 GB.

Well, the last one is SecureMMC. It is also based on the version 4.x specification that is used in MMC+. Its main feature is support for DRM protection. By the way, this is what originally distinguished the SD format from MMC. SecureMMC is an attempt to compete with SD. So let's move on to this standard.

The SD (Secure Digital) format is by far the most popular. It and its modifications are used everywhere: in digital players and cameras (even DSLRs), in PDAs and mobile phones. Probably the reason for this is its constant support and development from many companies.

SD was introduced in 1999 by Matsushita and Toshiba. A full-size Secure Digital card has the same dimensions as an MMC – 32x24x2.1 mm. The large thickness is explained by the presence of a write-blocking key. However, the SD specification allows you to make cards without it (they are called Thin SD), then the thickness is reduced to 1.4 mm.

Initially, the SD release aimed to compete with MemoryStick (discussed below), which supported DRM protection for media files. Then the development companies mistakenly assumed that the giants of the media industry would crowd online stores so much that all files would be protected by DRM. So we decided to make a fuss.

Secure Digital is based on the MMC specifications. This is why SD card readers easily work with MMC. Why not the other way around? To protect contacts from wear on SD cards, they were slightly recessed into the housing. Therefore, the contacts of a card reader aimed only at working with MMC simply will not reach the contacts of the SD card.

In terms of variety of formats, SD is no less “modest” than its predecessor. First of all, it is worth noting that two more form factors were presented: miniSD (20x21.5x1.4 mm) and microSD (11x15x1). The latter was originally created by SanDisk and was called T-Flash and then TransFlash. And then it was adapted as a standard by the SD Card Association.

The remaining differences relate to the card capacity. And there is some confusion here. It started with the first generation of cards, which reached a capacity of 2 GB. The SD card is identified by a 128-bit key. Of these, 12 bits are used to indicate the number of memory clusters and another 3 bits to indicate the number of blocks in the cluster (4, 8, 16, 32, 64, 128, 256 or 512 - a total of 8 values, which corresponds to three memory bits). Well, the standard block size for the first versions was 512 bytes. Total 4096x512x512 gives 1 GB of data. We've arrived.

When the lack of capacity “from above” began to tighten, version 1.01 of the specification appeared, which allowed the use of an additional bit to further determine the size of the block - it could now be 1024 or 2048 bytes, and the maximum capacity accordingly increased to 2 and 4 GB. But here's the problem - older devices could incorrectly determine the size of new memory cards.

In June 2006, a new edition of the standard appeared - SD 2.0. They even gave it a new name - SDHC or Secure Digital High Capacity. The name speaks for itself. The main innovation of SDHC is the ability to create cards up to 2 TB (2048 GB). The minimum limit is in principle unlimited, but in practice SDHC cards have a capacity of 4 GB or more. It is noteworthy that the maximum limit is artificially limited - 32 GB. For higher-capacity cards, it is suggested to use the SDXC standard (more about it below), although several manufacturers have introduced 64 GB SDHC.

The SD 2.0 standard uses 22 bits of data to define the size, but four of them are reserved for future use. So card readers that were not originally designed to work with SDHC will not be able to recognize new memory cards. But new devices can easily recognize old cards.

Along with the announcement of the SDHC format, identification by speed classes appeared. There are three options: SD Class 2, 4 and 6. These numbers indicate the minimum data exchange speed for the card. That is, a card with SD Class 6 will provide a speed of at least 6 MB/s. Well, the upper limit is naturally not limited, although so far the situation with SD cards is approximately the same as with CompactFlash - the fastest representatives have reached a speed of 300x or 45 MB/s.

It is worth adding that miniature form factors have also undergone modernization. Nobody has forgotten about miniSDHC and microSDHC. True, it’s mostly the first cards that come on sale. Today their maximum volume has already reached 16 GB, and 32 GB options are on the way.

Well, the latest innovation is the standard. Whether it was called version 3.0 or not, we were unable to find out. However, it differs from SDHC not so significantly. First of all, the artificial limitation on the maximum volume has been removed, which can now reach 2 TB. The maximum data transfer speed has been increased to 104 MB/s, and in the future they promise to raise it to 300 MB/s. Well, exFAT was chosen as the main file system (discussed below), while SDHC is content with FAT32 in most cases. The first SDXC cards have already been announced and they have a capacity of 32 or 64 GB. But products with their support will still need to wait for some time.

Actually, everything about SD cards. But within the framework of this standard, several more interesting things were released. For example, the SDIO (Secure Digital Input Output) specification. According to it, using the form factor and interface of SD cards, you can create devices such as GPS receivers, Wi-Fi and Bluetooth controllers, modems, FM tuners, Ethernet adapters, etc. That is, the SD slot in this case serves as a kind of analogue of USB.

SanDisk has distinguished itself with SD Plus cards, which immediately integrate a USB connector. Eye-Fi is a rather interesting development. This is a memory card with a built-in Wi-Fi controller. The latter can transfer data from the card to any computer. Thus, there is no need to even remove it from the camera or phone.

In total, today the Secure Digital format is the most popular and fastest growing. So far Sony is trying to resist it with its Memory Stick, but it’s not going well.

Memory Stick

Sony is known for its dislike of most formats and standards that were not developed by it. This is understandable - you won’t receive royalties from them. So eventually DVD+R/RW and Blu-ray and Memory Stick cards appeared. Introduced in October 1998, they are still distributed only among Sony products. And by and large, only Sony and a little SanDisk are involved in their production. The result of this is logical: relatively low prevalence and higher price than other flash cards of similar volume.

Over the entire existence of the Memory Stick, Sony has released as many as seven modifications. Moreover, unlike MMC, they are all in use. As a result, natural confusion arises, and at the same time, card reader manufacturers can increase the number of recognized standards by their products.

It all started with just a Memory Stick. This is an elongated memory card measuring 50x21.5x2.8 mm. Its shape somewhat resembles a piece of chewing gum. It was distinguished, as we wrote above, by DRM support, which was never required. Capacity varied from 4 to 128 MB.

Over time, this was not enough, and since an updated standard had not yet been developed, the Memory Stick Select format was announced. This is a regular Memory Stick card, but inside it there were two memory chips of 128 MB each. And you could switch between them using a special switch on the card itself. Not a very convenient solution. That's why it was temporary and intermediate.

We managed to cope with the low capacity by releasing Memory Stick PRO in 2003. Theoretically, such a memory card can store up to 32 GB of data, but in practice they were not made more than 4 GB. Of course, most older devices do not recognize the PRO version, but new ones can easily recognize the first generation Memory Stick. A sub-variant of the High Speed ​​Memory Stick PRO standard makes things even more confusing. All Memory Stick PROs with a capacity of 1 GB or more were like this. It is clear that they could operate in a special high-speed mode. And I’m very glad that they are all backwards compatible with older devices, but the speed dropped to normal.

Over time, it became clear that it would be necessary to go down the path of making cards smaller, otherwise Memory Stick “plates” are not convenient to use everywhere. This is how Memory Stick Duo appeared, measuring 31x20x1.6 mm - slightly smaller than Secure Digital. But bad luck, these cards were based on the first version of the Memory Stick standard, and with it a limitation on the maximum capacity. 128 MB for 2002 is somehow not at all respectable. This is how Memory Stick PRO Duo appeared in 2003. And it is this standard that is developing the most today - there are already 16 GB cards, 32 GB options are on the way, and the theoretical limit, according to Sony, is 2 TB.

In December 2006, Sony, together with SanDisk, announced a new modification of its flash memory cards - Memory Stick PRO-HG Duo. Its main difference from other options is its higher operating speed. In addition to the 4-bit communication interface, an 8-bit one has been added. And the controller frequency has increased from 40 to 60 MHz. As a result, the theoretical speed limit increased to 480 Mbit/s or 60 MB/s.

Well, following the latest fashion, in February 2006, the Memory Stick Micro card format (or it is also called M2) appeared, with dimensions of 15x12.5x1.2 mm - this is slightly larger than microSD. Their capacity varies from 128 to 16 GB, and theoretically can be 32 GB. Through an adapter, an M2 memory card can be inserted into the Memory Stick PRO slot, but if its capacity is more than 4 GB, certain recognition problems may arise.

This is such a squiggle. If you look at it, in principle it’s not difficult: Memory Stick is the original format, not the most compact in size, Memory Stick PRO is an option with greater capacity and speed, Memory Stick (PRO) Duo is a smaller version of cards, Memory Stick PRO-HG Duo is accelerated version of Memory Stick PRO Duo, Memory Stick Micro (M2) - the smallest Memory Stick. Now you can move on to the latest standard - xD.

xD-Picture Card

Olympus and Fujifilm felt that the flash card formats that existed in the early years of this century did not meet their ideas of ideal data storage for cameras. How else can we explain the development of our own xD-Picture Card standard?

From the name of the format it follows that it was created for storing images. But Olympus produces digital voice recorders based on it, and Fujitsu produces MP3 players. However, there are much fewer of the latest devices than cameras with xD support. However, if we compare the total sales volume of Fujitsu and Olympus digital cameras, they will in no way exceed the figures of the market leaders - Canon and Nikon. And the leaders quietly use CompactFlash in mid- and high-end SLR cameras, while the Secure Digital standard has taken root well in the rest. Well, since the distribution of xD cards is not very large, then in their development they lag behind the most popular formats, and besides, they are more expensive than them. About 2-3 times, if you take cards of the same capacity.

Obviously, the main focus of the developers of the xD format (by the way, Toshiba and Samsung are producing cards based on it) was to reduce the size of the memory card. Its dimensions are as follows - 20x25x1.78 mm. About the same as two Memory Stick Micros.

The capacity of the very first version of xD cards varies from 16 to 512 MB. They were presented in July 2002. However, in February 2005, the first update appeared, allowing the maximum volume to be increased to 8 GB. The new standard was called xD Type M. The volume was increased through the use of MLC memory, which at the same time turned out to be slower. Type M xD cards have reached 2 GB capacity. And so far this limit has not been overcome either by Type M or newer standards.

To solve the speed problem, xD Type H was introduced in November 2005. This format was based on SLC memory, since they decided to discontinue it in 2008 due to high costs. But it was replaced in April 2008 by the Type M+. Cards of this format are approximately 1.5 times faster than Type M.

Backwards compatibility of different versions of xD formats is true only for the newest devices - they can easily recognize older versions of cards. But older devices will not necessarily recognize the new cards. The situation here is approximately the same as with other standards.

As for speed, then, as in terms of volume, xD does not shine at all. Today, the average Type M+ read speed is 6.00 MB/s (40x), and write speed is 3.75 MB/s (25x).

In total, the xD-Picture Card format is more expensive in retail than SD and CF. Memory cards are quite compact, but their capacity no longer meets modern requirements. The same goes for speed. For shooting video with a resolution of 640x480 at 30 frames per second, Type M+ is still sufficient. But for today's SLR cameras, which shoot frames with a resolution of 12-24 MP and video in 720p and 1080p format, this is clearly not enough. It’s not bad at all to have a card for 200-300x. So we don’t see much point in continuing to support and develop xD. We also wouldn’t be surprised if they suddenly decide to close it down, and the next generation of cameras will be transferred to SD and/or CF.

The abbreviation SSD began to appear in news feeds and article titles relatively recently - a couple of years ago. The reason for this is that this technology began to become widespread only when flash memory began to be used more and more often for data storage, and the aforementioned news headlines (and text) spoke of the imminent rapid growth of this market, simultaneously promising the displacement of HDDs. At least from the laptop and netbook segment.

But the most interesting thing is that an SSD is not necessarily a flash memory drive. SSD or Solid State Drive means solid state drive. That is, the principle rather than the type is important here - “hard” memory is used to store data. A memory that doesn't spin, spin, or jump. So the SSD is not a couple of years old at all, but formally fifty years old. This technology was called differently then, but again, the principle is important here. But the principle has remained.

Today, two types of SSDs are relevant: based on volatile memory and based on non-volatile memory. The first are those that use SRAM or DRAM memory as their basis. They are also called RAM-drive. From time to time, such SSDs are announced by manufacturers as ultra-fast storage media. Some of them even allow you to independently increase the volume when connectors for conventional memory modules (DDR, DDR2 or DDR3 in the most modern version) are simply installed on the board.

Well, non-volatile memory is, of course, flash. It has been possible to create SSDs based on it for a long time, but the volumes of such drives were far from the capabilities of hard drives, and the cost was much higher. And the speed was not great. But today these shortcomings are gradually being eliminated.

The first generation of SSDs had capacities from 16 to 64 GB, and such “flash drives” cost hundreds and thousands of dollars. This was about two years ago. Today, 64-512 GB options are available at prices ranging from $200 to $1,500. It's a long way from hard drives, but much better. For and on the way, a 1 TB SSD in the format of a 2.5-inch hard drive. Let us remind you that mobile HDDs have not yet exceeded the capacity of 500 GB. And desktop ones have just reached the 2 TB mark. So SSD is moving forward by leaps and bounds.

As for the speed of work, it is also constantly growing. The first generation of SSDs lagged somewhat behind mobile hard drives, but modern drives have already surpassed them. Suffice it to recall the Intel X25-M SSD introduced last year, which has a read speed of 250 MB/s and a write speed of 70 MB/s. And it doesn’t cost as much as a flight to the ISS - about $350 with a capacity of 80 GB.

Of course, there are especially high-speed models from Fusion-IO with read/write speeds of 800/694 MB/s or PhotoFast G-Monster PCIe SSD with 1000/1000 MB/s, but they are priced like a small jet. And of course, for data exchange they use not SerialATA, but regular PCI Express x8 - this standard is still capable of providing the required bandwidth. By the way, PCI Express x1 is actively used to connect SSDs in netbooks. It is in this format that their data storage is made - in the form of a small PCI-E x1 card.

Such high speed performance for SSD drives was achieved thanks to parallel reading of data from several chips at once. For example, the Intel X25-M mentioned above works on the principle of a RAID level 0 array. That is, one bit is written to the first chip, the second to the second, and so on. It is extremely difficult to organize a similar mechanism for a regular USB flash drive or memory card, since they almost always only have one flash memory chip installed.

To increase capacity and reduce cost, MLC memory is often used in SSDs (including in the X25-M). More expensive models are equipped with SLC chips. But if you write data to a USB flash drive or some SD card relatively rarely, then to an SSD the recording is carried out continuously during operation. And in most cases you don’t even know it. Modern programs constantly maintain various logs; the operating system moves little-used data to the swap file, thus freeing up RAM; Even basic file access requires recording the access time.

So, in any case, you have to install more durable chips in the SSD. You also have to worry about algorithms for calculating the wear level and redistributing data - they must be more advanced than those of conventional flash drives. SSDs even have an additional volatile cache chip, just like a regular hard drive. The cache contains block address data and wear level data. When turned off, the latter are saved to flash memory.

In any case, for now, flash-based SSD technology continues to develop rapidly. It offers several undeniable advantages over HDD:

• significantly shorter data access time;
• constant data reading speed;
• zero noise level;
• less energy consumption.

At the moment, all that remains is to increase the number of rewrite cycles to such a number that you don’t have to worry about it at all. The capacity will continue to grow without that. It is possible that in the next 2-3 years it will catch up and even overtake hard drives. Well, the price falls by itself if the technology is promising, actively promoted and the level of sales is constantly growing. We don’t know whether SSDs will be able to supplant HDDs in the desktop computer market, but they are already moving towards mobile devices.

Future

Actually we have come to the end. The conclusion from the above can be drawn as follows: flash memory will become more widespread and improved in the future. It is not yet clear whether it will be able to replace hard drives, but it has the makings of this. But there is another catch - the file system.

Modern file systems are optimized for use with hard drives. But HDD is not an SSD at all in its structure. First of all, data on the hard drive is accessed using LBA addressing. A block of such an address allows you to calculate on which plate, on which track and in which sector the requested information is located. But here's the problem - flash does not have plates, tracks or sectors. But there are blocks divided into pages. Today this problem is solved by translating addresses from one format to another, but it would be much more convenient if all this happened directly.

Another feature of flash memory is that writing can only be done in previously cleared blocks. And this operation takes some time. It would be a good idea to clear completely unused blocks during idle time.

Modern disk file systems are optimized to minimize data access time - they try to ensure that they are searched as quickly as possible across the disk. But for flash memory this is simply irrelevant - all blocks are accessed equally quickly. Well, support for calculating the level of wear of flash chips from the file system would not hurt.

So the thing for the near future is the release of new file systems optimized for working with flash memory. These, however, already exist, but modern operating systems do not support them well. It is noteworthy that one of the first was FFS2 from Microsoft, which it released back in the early 90s.

Linux OS keeps up with progress. The file systems JFFS, JFFS2, YAFFS, LogFS, UBIFS were created for it. Sun also distinguished itself by developing ZFS, which recently . It is optimized not only for hard drives, but also for flash drives. Moreover, both for using them as the main storage and as a cache.

However, today the most popular file system for flash drives (not counting SSDs) remains FAT and FAT32. It's simply the most convenient. They are supported by all operating systems and do not require drivers. But they are no longer enough for work. For example, the limitation on the maximum file size (4 GB) is already becoming unacceptable.

However, Microsoft has a replacement - exFAT, formerly known as FAT64. As we already wrote, it was chosen as the main FS for SDXC cards. In addition to being optimized for flash memory, it supports files up to 16 exabytes (16.7 million terabytes) in size, and more than 65,536 files can be stored in one folder.

exFAT is supported today by the operating systems Windows Mobile version 6.0 and higher, Windows XP SP2 and higher, Windows Vista SP1, Windows Server 2008 and Windows 7 from build 6801. Note that in Windows Vista, an exFAT-based flash drive is not capable of being used as a cache in ReadyBoost functions. Corresponding support will appear in Windows 7. As for other operating systems, a free kernel module is available for Linux that allows you to use exFAT read-only.

So the most promising OS for flash drives today seems to be ZFS and exFAT. But both are very poorly distributed, although the latter has a better chance of becoming popular. It has already been chosen as the main one for the latest generation SD cards and all the most popular versions of Windows “know” it.

For the rest, we will wait for a further increase in the capacity of flash drives and a reduction in their cost. This technology is very good, so we wish it only success.

The search module is not installed.

A little about flash memory

Today, such a section (module, element - you can call it whatever you like) like flash memory is an integral part of almost all computer components (be it a sound card, hard drive, modem, magneto-optical drives or CD-ROM) that use memory in their work , and not only the computer (!). But what exactly is flash memory? This article is devoted to this and more.

Flash memory is a fairly important section in which updated programs and program modules are stored. Flash memory is used in a wide variety of systems, even BIOS, cell phones, pagers, etc. Using flash memory to store various parametric data not only improves the performance of a system, but also makes it possible to increase its reliability and reduce cost. For example, parametric flash memory blocks are widespread in modems, thanks to which the modem operates as an answering machine, and you can leave a message even when the computer is turned off. When it comes to cell phones, they use flash memory modules to store phone numbers, time tracking, user ID, and more. Flash memory is even used in cars in engine control systems and fuel delivery and rationing systems, keeping records not only of operation, but also of any problems that have arisen.

Flash Memory Module Technology

In operation, flash memory is comparable to computer RAM modules. Flash memory is modified electronically in the system. But unlike RAM, flash memory is non-volatile. Those. it works like a read-only memory unit and is capable of storing information and data for a long time even after the power is turned off. In addition, if information can be written to (and erased from) RAM one byte at a time, i.e., for example, as a whole file, then this does not happen when flash memory operates. All information is written and erased on the flash memory module byte by byte. And finally, the last difference is that in order to write information into RAM, you do not need to erase the previous one, because when new data is written, the old ones are automatically erased. On a flash memory block, you first need to delete old information, and then you can write new information.

Flash memory operation contains only three operations - write or program, read, erase. Each operation requires a certain amount of time. For example, it takes approximately 60 ns to read one parametric block, and 9 μs to write. The operation of erasing information takes on average from 0.6 to 4.5 seconds. This is the longest operation.

Programming flash memory is, so to speak, replacing a "1" with a "0", and erasing is replacing a "0" with a "1". The "0" and "1" in flash memory are blocks that have fixed addresses. Each block contains several cells in which information is located. When recording various information, the number of cells constantly changes. When erasing information on a flash memory module, the blocks themselves are erased. Erasing them entails deleting all the cells in the block.

Flash memory modules have a limited lifespan. But despite this, Flash Memory Boot Block chips (that’s what they are called) must withstand at least 100 thousand rewrite cycles at a voltage of 5 volts. One rewrite cycle is considered to be a completed cycle of writing and erasing operations of the same block of information with a volume of at least 8 KB. Naturally, much more information than 8 KB can be written to a microcircuit at a time, so the resource of the microcircuit depends not only on the rewriting cycle, but also on the volume of information being rewritten and on the frequency (periodicity) of its updating.

Special software methods and algorithms are used to record and erase information. They are used because it is impossible to delete a single cell from a block. Software algorithms help emulate byte rewriting using two 8 KB parametric blocks.

Structure of block (parametric) data in a microcircuit

In flash memory chips, for a more convenient organization of data in blocks, a special data structure has been developed, which is a form of linked lists. Each entry entered into this list consists of two fields. The first field contains the value of the parameter of the entry being entered. The second field specifies the address for the next entry of the same parameter. The first field is designated "Parameter". After "Parameter" there is a number, for example Parameter1. The list also contains ParameterX, which is, so to speak, a variable pointer that contains the address of the first entry of this parameter. If any cell of the block contains the value Parameter1, then this cell contains the address of the first parameter record, which contains the first value of Parameter1 and the address of the second Parameter1 record. The second entry, in turn, contains the last value of this parameter and the address of the third entry.

In the last record, usually in the "Next_Record" field, a code is entered, which is designated as FFh. It indicates that there are no more subsequent entries. This code represents the default value of the erased byte.

Due to the above, the process of writing information to flash memory or any change in parameters occurs as follows - the program finds the first free cell in some block, the new value is entered in the value field of the new record, and in order for the recording to be completed, the program updates the Next_Record field . Moreover, this field is updated in the previous record. The result is that each subsequent record has a connection with the previous one. Such structures and features of recording information are called linked lists.

When reading data, the program does not necessarily need to look through all the lists. Yes, this does not happen. The program simply finds the last value of this parameter and reads the necessary codes using its pointer.

The table below shows an example of the structure of the simplest linked list. In this example (the same applies to any other structure), Parameter_Value is variable and depends to a large extent on the specifics and volume of information entered.

Meaning	Address	Parameter
01H	Parameter1	Parameter1 Pointer Variable
03H	Parameter2	Parameter2 Pointer Variable
05H	Parameter3	Parameter3 Pointer Variable
F8H	01H	Parameter1 Value = F8H
07H	02H	Parameter1 Next_Record = 07H
22H	03H	Parameter2 Value = 22H
09H	04H	Parameter2 Next_Record = 09H
44H	05H	Parameter3 Value = 44H
FFH	06H	Parameter3 Next_Record = FFH = latest
55H	07H	Parameter1 Value = 55H
0BH	08H	Parameter1 Next_Record = 0BH
F2H	09H	Parameter2 Value = F2H
FFH	0AH	Parameter2 Next_Record = FFH = latest
F4H	0BH	Parameter1 Value = F4H
FFH	0CH	Parameter1 Next_Record = FFH = latest

Newer developments in flash recording technology add another parameter to the lists that only indicates that a particular parameter entry is the most recent (or updated). The field for this parameter is called "Parameter ID". To read in this case, the program is forced to go through (and read) each parameter until it “stumbles” on the last value of the parameter being viewed. But despite this, the use of this method is an alternative to the traditional method.

The process of writing or storing information can continue until there is no free space left in the flash memory module and until it is possible to write a complete complete parametric block. At the same time, there should be room for a complete recording. After filling the last block, in order for the lists to be coherent, the last value of each parameter is entered into the second block.

Clearing Flash Memory

Once the entire permissible volume of a flash memory block is completely filled, writing subsequent information into it, as mentioned above, becomes impossible. To do this, you must clear the flash memory.

Clearing a flash memory module involves erasing one, several, or all parameter blocks. In this case, the erasing process occurs due to the gradual rewriting and erasing of information. For example, in order to erase the first parametric block, the program needs to transfer information from it to the second block, and after that the first one is erased. Moreover, not all the information contained in the first block is transferred to the second block, but only the actual values ​​of the parameters related to subsequent blocks.

But even here there are some peculiarities! It was said above that up to 4.5 seconds are allocated for the process of erasing a parametric block. This is quite a lot for such an operation. In addition, when the system is running, there may not be that much time. However, erasing flash memory is not the main or only task performed by the system. Therefore, programs for working with flash memory provide a function to pause the erasing process. Erase pause is enabled in cases where the system needs to read data located in other parameter blocks. The command to pause erasing is given by the program that controls the flash memory module. When this program is executed, the module is in a suspended state. A similar example would be a computer freezing during operation. But in the case of flash memory, the “freeze” applies only to the erasing task (and besides, the program can continue this operation at any second), and as for reading, there are no barriers to this. After the system reads the data located in other blocks, the program sends a signal to the module (chip) to continue the erase operation. Erasing the parametric block will continue from the point where it was interrupted. But until the block erase operation is completely completed, it will be impossible to write new data in its place.

Perhaps in the future an algorithm will be developed that will allow new information to be recorded after erasing is suspended. But for now it is not there, and we have to be content with what we have.

In addition to all the listed nuances of flash memory, it also uses a certain amount of RAM.

In this regard, certain requirements arise for the system.

What is needed for full operation of flash memory?

The amount of RAM used when operating flash memory depends, first of all, on the nature and complexity of the module’s operating base embedded in the program. The program responsible for the operation of the flash memory module is divided into subroutines that each perform its own function. But it is not subroutines that are loaded into RAM, but the entire program. The code size of each subroutine (subroutines for writing, erasing, reading operations) ranges from 512 bytes to 1 KB.

Another weighty argument is that a program with an approximate volume of 15 KB is loaded into the flash memory module itself, and only 1..2 KB is unloaded into RAM.

Therefore, we can conclude that the first and rather significant requirement for the system will be the size of the RAM. For high-quality, full-fledged operation of the flash memory module (and the system as a whole), a minimum of 16 MB (and preferably 32 MB) is required.

For fast and stable operation, in addition to RAM, you must select the correct power mode. There are modules that operate on 3.3, 5 and 12 volts. Most modern modules are powered from a 12-volt source. Such voltage is necessary, in particular, for operations of intra-system erasing of information and its recording. But some 12-volt-oriented microcircuits are capable of operating from a 5-volt source. At the same time, the operation of flash memory at one and another voltage rating is no different. Such flash memory chips include, for example, modules of the Smart Voltage family.

Separately, I would like to dwell on flash memory oriented at 3.3 volts. Such modules are available in capacities up to 4 Kbit. They allow not only to improve the performance of devices, but also to optimize energy consumption. The technology for 3.3 volt flash memory modules was developed by Smart Voltage. This technology combines three parameters - low power consumption, the use of only one voltage rating and fairly fast programming. And all this is combined into one “device”.

If you compare a flash memory module designed for only 5 volts with voltages of 3.3 and 5 volts, the module with double the rating will be the best. Therefore, dual voltage flash memory performs write and erase operations much faster. For example, a block write is 10..13 µs, and a block write is 0.5..1 sec.

Another advantage of the dual power module is that it can be switched to 3 volt mode. This mode is mainly used on chips installed in cell phones and other portable equipment.

Unfortunately, during the process of reprogramming the flash memory module, power is lost during the update. Almost all manufactured modules have this problem. But manufacturers, producing their products, cope with it. When recording information, additional lines are added to parametric and block records. Typically these parameters are sections called "Parameter_Status". In this case, two bits are indicated in the parameter, one of which contains a code indicating the beginning of the parameter update, the other - the end of the update. As a result, the update end bit changes every second. If a power failure occurs, when it is restored, the program will receive data about the end of the update (where the process was interrupted) from the Parameter_Status section. When receiving information from the section, the program “knows” that an error occurred while executing the process and needs to be corrected.

Features of flash memory

When a flash memory module is running to perform write, erase, and read operations, it is necessary to determine the timing of these tasks. For this purpose, the microcircuit operating algorithm provides a dynamic characteristic.

The dynamic characteristic should not only provide calculation of the time to complete a certain task, but also take into account the delay time during the operation of both the device itself and the program. The calculation of the execution time, for example, of reading, depends on the length of the record of each parameter and on the number of these parameters. The length of the record and the number of parameters must be calculated before the record is made. From these calculations comes the total time for reading the data.

In addition, to perform each operation in RAM, you need to reload the program code located in the flash memory chip.

It is also necessary to calculate the total recording time, depending on the recording length and the number of recording parameters.

A dynamic characteristic is responsible for all this, which during operation greatly simplifies the operation of the flash memory module itself and the program that controls all operations.

New technology

All flash memory modules allow incremental (byte by byte) programming. A programming algorithm has now been developed at the bit level, i.e. recording bits or groups of bits in one session. The algorithm involves programming single bits by masking the rest.

The new technology not only saves module operating time, but also reduces the cost of flash memory.

AMD Flash Memory

Example of microcircuits (12 volt voltage)

Memory chip	Organization	Access time, ns
Am28F256A	32K x 8	70-200
Am28F512A	64K x 8	70-200
Am28F010A	128K x 8	90-200
Am28F020A	256K x 8	90-200

Flash Memory with 5V Programmability

Memory chip	Organization	Access time, ns	Number of pins
Am29F010	128K x 8	45-120	32
Am29F100	128K x 864K x 16	70-150	44, 48
Am29F200	256K x 8128K x 16	70-150	44, 48
Am29F040	512K x 8	55-150	32
Am29F400	512K x 8256K x 16	70-150	44, 48
Am29F080	1M x 8	85-150	44, 48
Am29F800	1M x 8512K x 16	85-150	40, 44
Am29F016	2M x 8	90-150	48

Flash Memory with 3V Programmability

AMD Flash Memory Specifications:

• supply current: 20-30 mA when reading and 30-50 mA when programming/erasing;
• current consumption in static mode: 25-90 mkA (CMOS mode), 1 mA (TTL mode);
• number of programming/erasing cycles: 100 thousand;
• information storage time: 10 years at 150°C, 20 years at 125°C;
• temperature operating conditions:
  • 0..+70°С (normal mode);
  • -40..+85°С (industrial mode);
  • -55..+128°С (extended mode).

Samsung plans - new flash memory coming soon!

According to Samsung Electronics' plans, gigabit flash memory will appear in the near future. Samsung's research laboratory has already created a prototype chip for a 1-gigabit flash memory module. In terms of size, the chip is only 0.15 microns thick (!). If you produce standard boards, then thanks to this chip they will fit a huge amount of information.

As Samsung promises, the new chip will soon go into mass production. Representatives of the company claim that it will be possible to record up to 500 photographs with a resolution of 1280 x 1024. And this is really a lot! Try creating 500 of these photos on your hard drive - see for yourself!

Based on such chips, Samsung Electronics plans to produce flash memory modules that will be used mainly (at first) in digital cameras and cameras. Perhaps, after the implementation of these plans, manufacturers will begin to produce memory for computer components. Manufacturers also claim that the production of their chips will immediately change the technology of producing flash memory throughout the world. In addition, manufacturers are going to (again based on this chip) develop memory modules with a capacity of 256 and 512 MB (!). Development studies are already underway. The new product, 1 gigabit flash memory, is planned to be released in 2001.

Conclusion

Flash memory is designed and used to simplify the operation of the system in which it is used, as well as improve its performance. By updating information via flash memory, the system (for example, modem, sound card, etc.) uses the computer's RAM to a much lesser extent. This increases the performance of not only one device, but also the entire computer as a whole.

Flash memory operates primarily by software-based byte-by-byte emulation techniques, using only two blocks of memory.

The use of flash memory chips also reduces hardware costs. Flash memory, using block architecture, has completely replaced erasable microcircuits.

In the process of creating and evolving computer technology, a lot of effort was spent so that the device could not only process information, but also reliably store it, both during the calculation process and in the form of final results.

Electronic memory can be divided into two main types - volatile and non-volatile. Despite the fact that volatile memory has good read/write speed characteristics, its contents are irretrievably lost when the power is turned off. Equipment designed to remember and store information after turning off the power, even for a long period (sometimes years), contains non-volatile memory.

For the purposes of long-term information storage, currently mainly two types of non-volatile memory are used - EEPROM and FLASH (see Fig. 1). And STMicroelectronics has remained the constant leader in the production of memory chips all this time. Let's look at the EEPROM and FLASH options using the example of microcircuits produced by this company.

Rice. 1.

Any memory chip meets the requirements of speed, storage time and cost. In addition, several points influence the choice of one type of memory or another:

The procedure for memorizing information:

• one byte of information at the right time;
• large blocks of information.

Memory access type:

• via parallel bus;
• via serial bus.

Additional requirements:

• the ability to read the contents of memory simultaneously with storing information;
• ensuring only authorized access;
• large amount of memory to store only data at the lowest cost;
• the ability to execute code directly from non-volatile memory (XiP).

There are microcircuits that have the best characteristics, such as:

• executing code in place,
• high degree of partitioning of the memory array with many supported special functions (presence of two ports, protected operating mode);
• non-volatile memory, but with the speed inherent in volatile ones;
• with a supply voltage less than 1.8 V;
• with an unlimited number of write/erase cycles.

However, the price of such a device will not be low.

If the main requirement for a device is to store limited amounts of information (sensor calibration tables, board serial numbers, small amounts of data [a few phone numbers for DECT, some status parameters, maybe even a few lines of code]), then a good solution for this case is EEPROM -memory that is used almost everywhere. In this case, as a rule, EEPROMs with a serial interface are used, because they are practically no longer produced with a parallel one. Such memory allows reprogramming of one arbitrary byte of information without the need for preliminary erasure. The ST range includes a wide selection of EEPROMs:

• volume from 1 Kbit to 1 Mbit;
• low consumption supply voltage ranges from 2.5 to 5.5 V and from 1.8 to 5.5 V;
• three standard serial buses I 2 C, SPI, MICROWIRE ®;
• 1 million write/erase cycles as standard;
• data storage time - more than 40 years;
• industrial and automotive temperature range;
• minimal landing pads, including MSOP8, TSSOP8 and uniquely sized UFDFPN8 (2x3 mm) housings.

On the table 1 shows the range of produced EEPROM memory.

Table 1. EEPROM memory chips

Name	Type interface	Size, kb	Voltage power supply, V	Range temperature, °C	Types buildings
M24xxx	I 2 C	128…512	1,8…5,5 2,5…5,5	-40…85 -40…125	SO8, MSOP8, TSSOP8
M24Cxxx	I 2 C	1…64	1,8…5,5 2,5…5,5	-40…85 -40…125	DIP8, SO8, MSOP8, TSSOP8
M24Mxxx	I 2 C	1000	1,8…5,5	-40…85	SO8
M93Cxxx	Microwire	1…16	2,5…5,5 4,5…5,5	-40…125	DIP8, SO8, TSSOP8
M93Sxxx	Microwire	1…4	2,5…5,5 4,5…5,5	-40…125	SO8
M95xxx	SPI	1…512	1,8…5,5 2,5…5,5	-40…85 -40…125	SO8, TSSOP8
M95Mxxx	SPI	1000	1,8…5,5	-40…85	SO8

If the main requirement is to store increased amounts of information (a large number of lines of code, a large amount of data), then the solution for this case is conventional FLASH memory (FLASH NOR). Parallel FLASH NOR is more common, but serial FLASH NOR is becoming increasingly popular in applications that do not have specific parallel access requirements (see Figure 2). For example, personal computer manufacturers have already chosen serial FLASH NOR as the main one. This trend of serial non-volatile memory (EEPROM and FLASH) can be seen in all existing applications (as well as in many new applications, such as digital consumer electronics).

Rice. 2.

Why serial interface?

• the cost of the controller is reduced, there are fewer pins;
• the space taken up on the printed circuit board and the size of the case are reduced;
• memory cost decreases (on average);
• flexibility in memory density increases (there is no need to change the board, if you need more memory, it is enough to install a larger memory crystal in the same seat);
• the content is loaded into RAM (program code storage) for execution.

The main directions of development of sequential memory are as follows:

• transition to high-density products;
• the need for high-speed serial data transfer;
• miniature, inexpensive case with a small number of pins.

In table 2 shows the available types and families of NOR FLASH memory.

Table 2. NOR FLASH memory chips

Kernel name microcircuits	Interface	Size, MB	Voltage power supply, V	Tempera- tour range, °C	Type housing
M29DWxxx	Parallel	32…128	2,7…3,6	-40…85	TFBGA48, TSOP48
M29Fxxx	Parallel	1…32	4,5…5,5	-40…85	PLCC32, TSOP32, SO44
M29Wxxx	Parallel	1…128	2,7…3,6	-40…85	TFBGA48, TSOP48
M28Wxxx	Parallel	16…64	2,7…3,6	-40…85	TFBGA48, TSOP48
M58LWxxx	Parallel	32…64	2,7…3,6	-40…85	TFBGA64, TSOP56
M25Pxxx	Consistent	0,5…128	2,7…3,6	-40…85	SO8, TSSOP8, SO16, VFQFPN8
M25PExxx	Consistent	1…16	2,7…3,6	-40…85	SO8, VFQFPN8
M45Pexxx	Consistent	1…16	2,7…3,6	-40…85	SO8, VFQFPN8

If the main requirement is to store increasing amounts of information, which is mainly data, then FLASH NAND is a better choice for this case. This memory is designed specifically for storing data. Storing program code in such memory is too dangerous due to possible errors during reading. Such memory is maintained in a special way: error correction is performed, unusable memory areas are marked, and the load is distributed across pages in the number of write/erase cycles. As a rule, all these functions are assigned to the control processor software.

The advantage of this type of memory is that it is relatively cheap in terms of the amount of available memory. ST produces FLASH NAND from 128 Mbit to 8 Gbit and more, with various page sizes: 528 bytes / 264 words and 2112 bytes / 1056 words, with memory density independent footprint, 1.8 V and 3 V power supply and in a variety of buildings.

NAND FLASH is also used in SD, Compact Flash, MMC memory cards, which are also produced by ST.

Separately, we can note a special type of memory that is produced by ST - the so-called NVRAM.

NVRAM is a non-volatile (thanks to a built-in lithium battery) static RAM device - a ZEROPOWER device with all its inherent properties such as writing speed and unlimited resource (M48Z family). The battery is connected to the chip package using SNAPHAT ® technology, an innovative and low-cost surface mount solution for ST products.

In addition, ST uses the same technology to produce TIMEKEEPER devices, which have a memory capacity from 1 kbit to 4 Mbit and also include a non-volatile real-time clock (M48T family). There are also feature-rich TIMEKEEPER Supervisors, offering useful features such as RTC, POR/LVD, Power-Fail Warning, Battery Monitor, Battery Switchover and Write Protection.

A complete list of memory chips offered by ST can be found on the website: http://www.st.com/stonline/products/families/memories/memory/index.htm.

Obtaining technical information, ordering samples, delivery -
e-mail:

Wide Application Motion Sensor

Company STMicroelectronics expanded its line of motion sensors with a new two-axis linear accelerometer with digital output. Micro-power miniature sensor LIS202DL, Possessing intelligent functions, it is designed for wide use, both in household appliances and for industrial applications.

The accelerometer has intelligent capabilities thanks to an integrated circuit and a high-frequency filter built into the sensor, which allows it to react and distinguish between impacts - single or double touch, and detect movement (moving, lifting). LIS202DL allows, for example, to turn off an inappropriately ringing phone in your pocket without taking it out - with one touch of your hand.

Tunable high-pass filters can be configured to monitor vibration or activate desired device functions through motion. The ability to implement specified functions due to external influences does not depend on the position in which the object under study will be at the time of measurements.

An ST sensor with built-in motion detection can be used to cut off power to a device that may turn on or off after movement (such as a remote control).

The digital output, implemented as standard SPI/I 2 C interfaces (can be selected), makes the sensor efficient to use and easy to integrate into the system.

The LIS202DL is housed in a miniature plastic case measuring 5x3x0.9 mm, which can be placed almost anywhere, limited by its small size.

Hi all! Today's article is entirely devoted to memory chips. Due to the enormous distribution and pace of development of various digital devices and gadgets, this type of microcircuit has become extremely widespread throughout the world. In almost every digital electronic gadget, be it a laptop, tablet, video camera, they are all connected by memory. We won’t go too deep into all these terms and cool buzzwords, we’ll just talk about the two main types of memory, RAM and ROM.

These two types of memory chips are always used together in electronics, ROM (read only memory) is a place for non-volatile data storage, or EEPROM in another. RAM (random access memory) is almost the same, only the data is stored there until the power is turned off, after turning off the power again - all information is lost on RAM chips, while on ROM chips information can be stored for a very long time, and when the power is turned off, the information is not deleted.

The first type of microcircuits (EEPROM, ROM)

A solid-state data drive is used for permanent data storage, with the ability to repeatedly rewrite information, repeatedly read it and store it for a long time, both with and without power. In everyday life - ROM is used in all kinds of drives, flash cards, SSD hard drives, even in our favorite microcontrollers as a storage area for “firmware”. Microcontrollers are essentially ROM and a microprocessor that executes commands from the firmware file, all in one package, on one chip. If you used RAM instead of ROM, after each shutdown you would have to flash and load data (and this is the same thing), and if vice versa - ROM instead of RAM, using such memory, even if it was 32 GB, it would be enough for you for 5 minutes, nothing more, a kind of RAM is a clipboard between the device sending information and the device receiving it.

The second type of memory chips

(RAM, also known as RAM) - solid-state data drive, RAM - random access memory, where files are temporarily loaded for the OS to work (service processes are always active and occupy part of the RAM) and what the OS works with, be it a game, a video, your favorite song or something else, a DVD player works on the same principle, loading information from an optical disk into RAM and then being silently read by the processor. Haven’t you noticed how a DVD player once stood silently, and the picture with sound was quietly reproduced? - this approach is used to ensure that there are no errors during reading, the data is read and the checksum is compared. The computer’s HDD drive and other devices that read data from optical disks, etc., work on this principle...

Let's look at this in more detail, using a tablet as an example.

1. The power controller, its purpose is clear, to power everything this miracle.
2. CPU. It ties everything together, performs all system functions, is controlled by the software interface, while the user controls the operating system, the OS is already the processor. In computers and laptops, the connecting role between hardware and software is played by the BIOS chip (basic data input/output system. (My nickname was not chosen easily! =))
3. A read-only memory chip, a ROM, is divided into two parts systemically, one part contains service information, and the operating system. And in another part of it there is memory available directly to the user.
4. RAM chips, everything is clear, RAM, “enough” files on the fly, the requirements from this memory are high data exchange speed and the fastest possible rewriting. That’s why “operational” - it must work efficiently))).

As you can see, there is nothing really complicated, only their manufacture is complicated, although lately there has been a lot of competition in the memory market. The undoubted giants in its production are three corporations, the South Korean corporation SAMSUNG and Hynix (Hyundai Electronics), and the American Kingston. But they are also produced by other corporations, for example Intel, MEDIATEK, Quanta and many others; sometimes there are even “but name” microcircuits, and who made them will remain a mystery.

A storage device is essentially a cell with a huge number of transistors in which the value “1” or “0” is stored; if the binary system is simple, there is a charge on the transistor - this is “1”, no charge - “0”, in inversion it turns out the other way around.

Next we’ll talk only about ROM, flash and other EEPROM

If the microcircuit is an MMC/SD type, then this is the most common “flash drive” of an SD interface and it already includes a controller and memory, in fact it’s just a flash drive that has a different casing. on the Internet there is an example of a successful replacement of the Hynix H26M52002CKR microcircuit with a regular microSD card on a Nokia 808 mobile phone.

I became very interested in all this, and at that very moment such a simple adapter-card reader was soldered together.

Connects to any compatible computer.

How to connect this whole thing? First, you need to find out the pinout of the card reader:

The pinouts of memory cards and card readers of interest can be viewed on the Internet. But where can I see the pinout of BGA and TSOP microcircuits?

Everything is there, on the Internet, or rather in the datasheet downloaded for a specific microcircuit; in the datasheet, by the way, there is everything, from the supply voltage to the type of microcircuit.

Look carefully at the type of your microcircuit - if MMC/SD and SD in general are combined, then everything should work out, but if it’s just NAND memory, then you need to install a controller, such as on USB flash drives and on SD/microSD (SDHC) already installed.

By the way, the finished controller can be used from the same USB flash drives.

Good luck to everyone in interesting experiments, be careful and don’t burn anything! Please write to the conference about the results. Author of the material - BIOS.

Discuss the article MEMORY CHICKS

Fundamentally, memory chips are divided into non-volatile, which do not lose information when the power is turned off, and volatile, the contents of which are considered uncertain every time they are turned on. The first of them are designed to store programs, constants, tables and other data that does not change or rarely changes, and is called ROM (read-only memory). The latter are intended for temporary storage of data arising during the operation of the device, and are called RAM (random access memory). In turn, ROMs are classified according to the method of entering information and the method of erasing it, if only such a possibility exists in a given class of ROM. The cheapest recording method is mask programming during the manufacturing process of the crystal. Memory chips with<прошитой>information - ROM (Read Only Memory) - cannot be reprogrammed, and they are used only in mass production, large quantities and guaranteed error-free text. The next type of ROM - PROM (Programmable Read Only Memory) - comes in<чистом>form and provides the user with the opportunity to independently, using the programmer, enter the required content. If this process is irreversible, then such microcircuits are called OTP (One Time Programmable) - once programmable. If it is possible to clear the contents and then add new ones, then the chips are called EPROM (Erasable Programmable Read Only Memory). Finally, depending on the erasing method, they can be either UV-EPROM, ultraviolet erasable, or EEPROM, electrically erasable. However, the terminology that has developed in recent years more often uses the abbreviation EEPROM for a certain type of memory, which, in a sense, can be considered non-volatile RAM.
Actually, electrically erasable ROM is usually called Flash memory. The differences between them are quite large. EEPROM allows random access to memory cells when writing, Flash memory allows only page access, that is, broken down into sectors, when erasing/writing. It is impossible to rewrite the contents of a single memory cell. When reading, there is no fundamental difference between them. In addition, programming Flash memory is a whole process that requires additional software steps to put the chip into programming mode and control its completion. As a result, the scope of Flash memory is program texts, tables and other data, the changes of which are either not expected at all, or are allowed, but very rarely. EEPROM memory is used for current storage of data during operation, when changing constants and settings (for example, on a TV), with automatic saving when the power is turned off. At the same time, Flash memory has a larger capacity and a lower price when converted to the cost of storing one byte of information.
Random Access Memory (RAM) is fundamentally divided into two types: static - SRAM and dynamic - DRAM. The first, in the presence of supply voltage, can store recorded information for as long as desired without any access to it. The storage cell is a trigger. The second requires constant<регенерации>, that is, reading and re-writing to the corresponding cells. This is due to the physical basis of storage, which in DRAM is a negligible capacitor connected at the intersection of the rows and columns of the matrix. This achieves ultra-high packaging density and large specific information capacity of the microcircuit. The cost is the need to periodically carry out a regeneration cycle. You also have to sacrifice energy consumption. DRAM chips are used today almost exclusively in computers and other computing equipment.
Of greater interest to us are SRAM microcircuits, which, in turn, are divided into micro-power with a relatively low speed (55 - 120 ns) and high-speed (7 - 25 ns) with significantly higher power consumption.
There are other types of RAM, for example, “Zero-Power” with a built-in lithium battery or “Dual-Port” with a different information access system.

Main parameters of memory chips:

information capacity. The ability to store a certain number of bits of binary information; organization of memory chips. It can be different with the same amount of memory. For example, 65,536 bits might look like 4,096 x 16, or 8,192 x 8, or some other combination. The internal organization of the memory matrix remains unchanged, only the external interface and, accordingly, the number of external pins change;

sampling time. Time from the submission of the last signal allowing reading until stable data appears at the output; power consumption. As always, there is a trade-off between power consumption and chip speed; supply voltage. The general trend towards a decrease in supply voltage has led to the emergence of memory chips operating at 3.3, 2.5 and even 1.8 volts; temperature Range. Commercial, industrial or advanced.

Specific memory parameters include the following: storage time(hours, years), number of rewrite cycles, erase time and others.

In conclusion, it should be noted that EEPROM and Flash type chips often have a serial external data exchange interface. This significantly reduces the exchange speed, but in those applications where it is not critical, it allows you to save the number of external pins of microcircuits, the area occupied on the printed circuit board, and the number of solders.