What is Flash memory to explain to children. Useful amount of flash drives: What is it? The main characteristics of the USB drive
What is Flash Memory?
Flash Memory / USB Drive or Flash Memory- This is a miniature storage device applicable as an additional media of information and its storage. The device is connected to a computer or other reader through the USB interface.
The USB drive is designed for multiple read information recorded on it during the established period of operation, which is usually from 10 to 100 years. You can make a limited number of times on flash memory (about a million cycles).
Flash memory is considered to be more reliable and compact compared to hard disks (HDD), since it does not have mobile mechanical parts. This device is quite widely used in the production of digital portable devices: photo and video cameras, voice recorders and MP3 players, PDAs and mobile phones. Along with this, Flash Memory is used to store the built-in software in various equipment, such as modems, mini-PBX, scanners, printers, or routers. Perhaps the only drawback of modern USB drives is their relatively small volume.
History Flash Memory
The first flash memory appeared in 1984, it invented the engineer of Toshiba Fujio Masuoka, whose colleague Söji Ariidzumi (Shoji Ariizumi) compared the principle of this device with a photo message and first called it "Flash". Public presentation Flash Memory took place in 1984 at the International Seminar on electronic devices, California, which was held in San Francisco, California, where the Intel was interested in this invention. Four years later, her specialists released the first flash processor commercial type. The largest manufacturers of flash drives at the end of 2010 were Samsung, which occupies 32% of this market and Toshiba - 17%.
The principle of operation of the USB drive
All information recorded on the Flash drive and stored in its array, which consists of transistors with a floating shutter, called cells (Cell). In ordinary devices with single-level cells (Single-Level Cell), any of them "remembers" only one data batch. However, some new chips with multi-level cells (Multi-Level Cell or Triple-Level Cell) are able to remember and more information. At the same time, a different electrical charge should be used on a floating shutter of the transistor.
The main characteristics of the USB drive
The volume of the currently presented flash drives is measured from several kilobytes to hundreds of gigabytes.
In 2005, Toshiba and SanDisk specialists held a presentation of the Nand-processor, the total volume was 1 GB. When creating this device, they applied multi-level cell technology when the transistor is able to store several data bits using a different electrical charge on a floating gate.
In September next year, Samsung presented the public already a 4-gigabyte chip, developed on the basis of the 40-nm of the technological process, and at the end of 2009, Toshiba technologies declared the creation of 64 GB of a flash drive, which was launched in weight production at the beginning of the following of the year.
In the summer of 2010, a presentation of the first USB-drive of 128 GB, consisting of sixteen modules of 8 GB, took place.
In April 2011, Intel and Micron announced the creation of the MLC NAND flash chip on 8 GB, with an area of \u200b\u200b118 mm, almost half of the same devices, which started the serial production at the end of 2011.
Types of memory cards and Flash drives
It is used mainly in professional video and photo-equipment, because it has quite large dimensions of 43x36x3.3 mm, as a result of which it is quite problematic to install a compact flash slot into mobile phones or MP3 players. At the same time, the card is considered not very reliable, and also does not have a high data processing rate. The maximum allowable amount of Compact Flash currently reaches 128 GB, and the data copy speed rose to 120 MB / s.
RS-MMC / REDUCED SIZE MULTIMEDIA CARD- Memory card, which twice the length is less than the standard MMC card - 24x18x1.4 mm and weighing about 6 grams. At the same time, all other characteristics and parameters of the usual MMC card are saved. To use RS-MMC cards, you must use an adapter.
MMCMICRO. - miniature memory card with sizes of only 14x12x1.1 mm and intended for mobile devices. To use it, you must use the standard MMC slot and a special adapter.
Despite very similarly with MMS-card, the parameters and dimensions of 32x24x2.1 mm, this card cannot be used with the standard MMS slot.
SDHC / SD HIGH CAPACITY - This is a high-capacity SD memory card, known to modern users like SD 1.0, SD 1.1 and SD 2.0 (SDHC). This device differ in the maximum allowable amount of data that can be placed on them. This is how 4 GB capacitance limitations are provided for SD and 32 GB for SDHC. In this case, the SDHC card is compatible with SD. Both options can be represented in three physical dimensions: standard, mini and micro.
microSD / Micro Secure Digital Card - This is the most compact data for 2011 removable devices Flash memory, its dimensions are 11x15x1 mm, which allows you to use its mobile phones, communicators, etc. The recording protection switch is located on the MicroSD-SD adapter, and the maximum possible amount of the card is 32 GB.
Memory Stick Micro / M2 - Memory card, the format of which competes in size with MicroSD, but at the same time the advantage remains for Sony devices.
Preface
New Year - Pleasant, bright holiday, in which we all sum up the year of the past, look with hope for the future and give gifts. In this regard, I would like to thank all the chairs for support, help and interest shown in my articles (,,,). If you once did not support the first, there was no subsequent (already 5 articles)! Thank you! And, of course, I want to make a gift in the form of a scientific and popular-cognitive article on how fun can, interestingly and with benefit (both personal and public) use rather severe analytical equipment at first glance. Today, under the New Year, there is a USB-flash drive from A-DATA and SAMSUNG SO-DIMM SDRAM module.Theoretical part
I will try to be extremely brief so that we all have time to prepare Olivier salad with a margin for a festive table, so part of the material will be in the form of links: Wear - read at leisure ...What memory is there?
On the currently There are many options for storing information, some of them require constant feeding with electricity (RAM), some forever "stitched" into the control chips around us (ROM), and some combine the qualities and those and others ( Hybrid). To the latter, in particular, and belongs to Flash. It seems to be non-volatile memory, but the laws of physics are difficult to cancel, and periodically on flash drives to overwrite the information after all.The only thing that, perhaps, can combine all these types of memory are more or less than the same principle of operation. There is some two-dimensional or three-dimensional matrix, which is filled in 0 and 1 to about thus thus and from which we can subsequently can or be considered or replaced, i.e. All this is a direct analogue of the predecessor - memory on ferrite rings.
What is Flash memory and what it happens (Nor and Nand)?
Let's start with Flash memory. Once upon a time he was published a fairly on the wrong IXBT, which is Flash, and which 2 main varieties of this type of memory are. In particular, there is NOR (logical non-or-orn) and nand (logical not-i) Flash memory (everything is also described in detail), which are somewhat different in their organization (for example, NOR - two-dimensional, NAND can be three-dimensional), But have one common element - a transistor with a floating shutter.
Schematic representation of a transistor with a floating shutter.
So, how does this miracle of engineering thought work? Together with some physical formulas, this is described. If briefly, then between the control shutter and the channel, by which the current flows from the source to the drain, we place the fastest shutter, surrounded by a thin layer of dielectric. As a result, when the current flow through such a "modified", the field transistor is a part of the high energy electrons tunneling through the dielectric and turn out to be inside the floating shutter. It is clear that while the electrons tunneled, they wandered inside this shutter, they lost part of the energy and will not return to almost return.
NB:"Practically" is a key word, because without overwriting, without updating the cells, at least once a few years, Flash "is reset" as well as the RAM after turning off the computer.
Again, we have a two-dimensional array, which you need to fill 0 and 1. Since the accumulation of charge on a floating shutter is a fairly long time, then in the case of RAM, a different solution is applied. The memory cell consists of a condenser and a conventional field transistor. At the same time, the condenser itself has, on the one hand, a primitive physical device, but, on the other hand, is nontrivially implemented in the gland:
Device RAM cell.
Again, IXBT has a good dedicated to DRAM and SDRAM memory. She, of course, is not so fresh, but the principal moments are described very well.
The only question that torments me is: Does DRAM have, how are Flash, Multi-Level Cell? It seems yes, but still ...
Part practical
Flash.
Those who use flash drives for quite a long time, probably have already seen a "naked" drive, without a housing. But I still briefly mention the main parts of the USB-Flash drive:
The main elements of the USB-Flash drive: 1. USB connector, 2. Controller, 3. PCB-multi-layered printed circuit board, 4. NAND MODULE, 5. Quartz reference frequency generator, 6. LED indicator (now, however, there is no on many flash drives), 7. No write protection switch (similar to many flash drives), 8. Place for Additional memory microcircuit.
Let's go from simple to complex. Quartz generator (more about the principle of operation). To my deep regret, during polishing the quartz plate itself disappeared, so we can only admire the case.
Quartz generator case
By chance, between the case, found, what the reinforcing fiber looks like inside the textolite and balls, of which they are in the mass and consists of textolit. By the way, and the fibers are still laid with a twist, it is clearly visible on the top image:
The reinforcing fiber inside the textolite (red arrows indicate fibers perpendicular to the slice), from which the main mass of the textolite consists
And here is the first important part of the flash drive - the controller:
Controller. The top image is obtained by a combination of several sam microphotography
I admit honestly, I didn't quite understand the idea of \u200b\u200bengineers who in the fill of the chip were put on some other additional guards. Maybe it is from the point of view of the technological process easier and cheaper to do.
After processing this picture, I shouted: "Yayayayasha!" And ran around the room. So, to your attention is a 500 nm technical process in all its glory with perfectly drawn flow boundaries, the source, control shutter and even the contacts are preserved in relative integrity:
"Ide!" Microelectronics - TEhProcess 500 nm of the controller with perfectly drawn separate drains (DRAIN), sources (Source) and control shutters (GATE)
Now proceed to dessert - memory chips. Let's start with contacts that this memory in the literal sense of the word feeds. In addition to the main (in the figure of the "thick" contact itself) there are also many small. By the way, "fat"< 2 диаметров человеческого волоса, так что всё в мире относительно:
SEM images of contacts that feed the memory chip
If we talk about memory itself, then success is also waiting for us. It was possible to select individual blocks, the boundaries of which are highlighted by arrows. Looking at the image with a maximum magnification, try to strain the look, this contrast is really difficult to distinguish, but it is in the image (for clarity I noted a separate cell lines):
Memory cells 1. Blocks of blocks are highlighted by arrows. Lines indicated separate cells
I first, first it seemed like an artifact image, but finishing all the photos of the house, I realized that these were either pulled by a vertical axis of control shutters with a SLC cell, or these are several cells collected in MLC. Although I mentioned MLC above, but still this is a question. For reference, the "thickness" of the cell (that is, the distance between two light points on the lower image) is about 60 nm.
In order not to smell - here are similar photos from the other half of the flash drive. Fully similar picture:
Memory cells 2. Block boundaries are highlighted by arrows. Lines indicated separate cells
Of course, the chip itself is not just a set of such cell cells, inside it there are some other structures whose belonging to me could not be determined:
Other structures inside the NAND memory chips
Dram.
I, of course, did not cut the whole SO-DIMM fee from Samsung, only one of the memory modules was not separated from the construction dryer. It is worth noting that one of the advice was useful here, proposed after the first publication - to cut at an angle. Therefore, for a detailed immersion in the seen it is necessary to take into account this fact, especially since it cut at 45 degrees, it has also allowed to obtain a "tomographic" condenser sections.However, by tradition, we will start with contacts. It was nice to see what the "Skol" BGA looks like and what the soldering itself represents:
"Skol" BGA-soldering
But the second time it's time to shout: "Survo!", So it was possible to see individual solid-state capacitors - concentric circles in the image marked by the arrows. It is they who store our data while working in the form of charge on their plates. Judging by the photographs, the size of such a capacitor is about 300 nm wide and about 100 nm in thickness.
Due to the fact that the chip is cut at an angle, some capacitors dissected carefully in the middle, and others are cut only "Boc":
DRAM memory in all its glory
If someone doubts that these structures are capacitors, you can see more "professional" photo (though without a large-scale label).
The only moment that I was embarrassed that the capacitors are located in 2 rows (left under the bottom photo), i.e. It turns out that 1 cell accounts for 2 bits of information. As mentioned above, information on multibite record is available, but as far as this technology is applicable and used in the modern industry - remains for me.
Of course, in addition to the memory cells themselves inside the module there are also some auxiliary structures, about the purpose of which I can only guess:
Other structures inside DRAM-memory chip
Afterword
In addition to the references that the text, in my opinion, is quite interesting by this review (albeit from 1997), the site (and photo gallery, and chip-art, and patents, and a lot of everything) and this office, which actually engaged in reverse engineering.Unfortunately, a large number of video on the topic of Flash and RAM production was failed, so you can only be content with USB-Flash-drives assembly:
P.S.: Once again, with the upcoming New Year of the Black Water Dragon !!!
It turns out strange: the article about Flash wanted to write one of the first, but fate ordered otherwise. Crossing fingers, let's hope that the next 2, articles (about bio-objects and displays) will be seen in the early 2012. In the meantime, the seed is carbon tape:
Carbon scotch, on which the test samples were fixed. I think that the usual tape looks like
The concept of building a device remained unchanged since 1995, when Flashki first began to be made on an industrial scale. If you do not delve into the details, the USB flash card consists of three key items: * USB connector - well-known to each connector, which is an interface between flash and computer system, be it system personal computer, multimedia center or even car radio; * Memory controller is a very important chain element. Communicates with the memory of the device with the USB connector and manages the data transfer in both directions; * Memory chip is the most expensive and important part of the USB flash card. Determines the amount of the information on the information map, the speed of reading / writing data. What can change in this scheme? It is fundamentally nothing, but the modern industry provides several options for such a scheme; Combination of ESATA and USB connectors, two USB connector.
1 - USB connector; 2 - microcontroller; 3 - control points; 4 - flash memory microcircuit; five -- quartz resonator; 6 - LED; 7 - Switch "Record Protection"; 8 - place for an additional memory chip.
Operating principle
Flash memory stores information in an array of transistors with a floating gate, called cells (eng. Cell). In traditional devices with single-level cells (eng. Single-Level Cell, SLC), each of them can only store one batch. Some new devices with multi-level cells (eng. Multi-Level Cell, MLC; Triple-Level Cell, TLC) can store more than one bit using different levels electric charge On a floating shutter of the transistor.
Types of flash memory
NOR.
At the heart of this type of flash memory lies or non-element (eng. NOR), because in the transistor with a floating shutter, the low voltage on the gate indicates a unit.
The transistor has two shutters: control and floating. The latter is completely isolated and able to hold electrons up to 10 years. There are also stock and source in the cell. When programming a voltage in the control gate, an electric field is created and a tunnel effect occurs. Part of the electrons tunnels through the layer of the insulator and falls on the floating shutter. The charge on the floating shutter changes the "width" of the channel of the stock source and its conductivity, which is used when reading.
Programming and reading cells differ greatly in power consumption: Flash memory devices consume a sufficiently large current when recording, while when reading energy costs are small.
To erase information, a high negative voltage is supplied to the control shutter, and the electrons from the floating shutter are transmitted (tunneling) to the source.
In NOR-architecture, each transistor needs to bring individual contact, which increases the size of the circuit. This problem is solved with the help of Nand-architecture.
Nand.
Nand-type is based on it is not an element (eng. Nand). The principle of operation is the same, from NOR-type differs only by the placement of cells and their contacts. As a result, it is no longer required to bring individual contact to each cell, so the size and cost of the Nand-chip can be significantly less. Also, recording and erasing happens faster. However, this architecture does not allow access to an arbitrary cell.
NAND and NOR-architectures now exist in parallel and do not compete with each other, as they are used in different storage areas.
Today, manufacturers produce drives on flash memory multiple types: these are cardsCompact Flash, SmartMedia, Multimedia Card, SecureDigital Card, Memory Stick and USB.
ATAFlash.. The first storage devices on flash memory that appeared market were cardsATA Flash. . These drives are made in the form of standard mapsPC Card . In addition to the flash memory chip in them, an Ata controller is installed in them, and during operation they emulate the usualIDE -disk. Interface of these cards parallel. CardsATA Flash. Not widespread and are currently used extremely rarely.
Compact.Flash.. Compact Flash (CF ) were offered by the companySanDisk As a more compact and convenient alternative to the cardsATA Flash. . Therefore, the developers of the StandardCF. have the opportunity to work these cards as devicesPC Card or as IDE -Efigure. In the first case, the cards work as ordinaryPC Card Devices and their interface "turns" into the tirePC Card . In the second - as toughIDE -Disci and their interface works like an Ata bus.
CF cards For the first time appeared in 1994. All maps of this type have a 50-pin parallel interface. By the way, there are cardsCF. Two types - TourI and TURE II . Cards type TourII. two millimeters thicker and appeared only because before the chassis of cardsI. did not allow to post inside the FLASH memory of a large volume for the manufacture of spacious carriersCF. . Currently, there is no such need and cards roundII. Gradually go from the market. Note that in drives for cardsII. You can install cardsI. , while the reverse is impossible.
Among flash cards, the undisputed leader in performance wasCF-Cart Transcend Ultra Performance 25 x CompactFlash 256 MB, which can be rightfully considered the benchmark for the rate of modern flash drives. The speed of the serial / random recording of this flash card reaches 3.6 / 0.8 MB / s, read speed - 4.0 / 3.7 MB / s.
CF speed -Cart slows down with an increase in volume, which is clearly seen by the Flash Card Example 512 MB. Two-time growth of the capacity leads to a decrease in productivity by 30%. With the exception of the random recording rate, which increased by 2.5 times, it looks rather strange and unexpected.
Speed \u200b\u200bcharacteristicsCF. -Carts are also strongly dependent on the manufacturer. W.Kingston CompactFlash. 256 MB - low speed Entries (serial / random recording - 1.4 / 0.3 MB / s), but at the speed of reading it was the leader (4.4 / 3.8 MB / s). MapPQI HI - Speed \u200b\u200bCompact Flash 256 MB demonstrated average performance in both cases: recording - 2.1 / 0.7 MB / s, reading - 3.8 / 3.3 MB / s. CardsSanDisk CompactFlash 256 MB and SanDisk CompactFlash 512 MB worked very slowly: recording - 1.1 / 0.2 and 0.9 / 0.5 MB / s, reading - 2.3 / 2.1 and 1.8 / 1.7 MB / s. And map 256 MB recorded and read the data equally well.
If comparing CF. -Maps with other types of drives, it turns out that flash memory is completely at such a slow, as is customary! In terms of performance, the fastest flash memory samples (as a reference, take the mapTranscend Ultra Performance 25x CompactFlash 256 MB) comparable withIomega Zip. 750 MB, and in the speed of the serial record even overtake this drive more than 1.5 times! For the speed of the sequential record, flash memory overtakes discsCD - RW. 2 times, by the speed of consistent reading - by 10%! Flash memory benefits from the SEVER speed of a serial recording - 2 times - and random reading - by 10%, but lags behind the speed of consistent reading and random recording - by 20%. Flash memory lags behind the speed of consistent entry fromDVD. - Discovers (with "bombing" in 4x mode) - 1.4 times.
Note that ifCF. -case is used in a digital camera, then the speed is primarily important for it. consistentrecords - what it is higher, the faster the camera will return to the working condition after the "capture" of the frame and the "reset" of it on the flash card. However, read speedCF. -Carts are also important in this case, the truth is not as critical - the faster the data is read, the faster the camera will work in the mode of viewing the footage.
SmartMedia. . Construction of cardsSmartMedia (SM. ) Extremely simple. In the mapSM. There is no built-in interface controller and in fact - it is one or two flash memory chips, "packed" in the plastic casing. StandardSM. was developed by companiesToshiba and Samsung In 1995, the card interfaceSM. - Parallel, 22-pin, but only eight lines are used to transfer data.
Multimedia. Card . Multi-Media Card (MMC ) have a 7-pin serial interface that can operate at a frequency up to 20 MHz. Inside the plastic case, the flash memory microcircuit and the MMS interface controller is placed. The MMS standard has been proposed in 1997 by companies.Hitachi, SanDisk and Siemens.
SecureDigital. Card . SecureDigi - Tal Card (SD ) - the youngest Flash Card Standard: It was developed in 2000 by companiesMatsushita, SanDisk and Toshiba. Actually sd. - this is the further development of the MMS standard, so MMS cards can be installed in drivesSD. (The opposite will be incorrect). InterfaceSD. - 9-pin, sequential-parallel (data can be transmitted one by one,two or four lines at the same time), operates at a frequency up to 25 MHz. CardsSD equipped with Pe. a record for protecting their recording content (the standard also provides modification without such a switch).
USB - Flash memory. USB-Flash memory (USB -Pasy) - a completely new type of media on flash memory, which appeared in the market in 2001uSB form -Pamil reminds the keychain of the oblong form consisting of two halves - a protective cap and the actual drive withUSB -Blease (inside it is placed one or two flash memory chips andUSB controller).
Work with usb - Family is very convenient - no additional devices are required for this. Enough to have a PC under handWindows with unoccupied USB -Port so that in a couple of minutes "get to" to the contents of this drive. In the worst case you will have to install driversUSB -pamyti, in the best - newUSB -Thiste and logical disk will automatically appear in the system. Possible in the futureUSB - Will it become the main type of device for storing and transferring small amounts of data.
As for USB -Flash memory, it is undoubtedly a more convenient solution for transferring data than flash cards - no additional flash drive is required. However, the performance of tested drives of this type -Transcend Jetflash 256 MB and Transcend Jetflasha 256 MB - limited low throughput InterfaceUSB 1.1. Therefore, their indicators in the tests for the speed of work were rather modest. If aUSB Flash memory to equip a quick interfaceUSB 2.0, then on "rainfreight" these drives, of course, will not yield to the best flash cards.
It is interesting to note that the speed of the sequential write flash memory exceedsIomega Zip 750, CD wheels - RW and my carriers and is inferior onlyDVD. -Disc. This once again emphasizes that flash memory developers first of all sought to increase speed consistententries, since flash memory is initially intended for use in digital cameras, where this indicator is primarily important.
As a result, it is possible to conclude that flash memory is an undisputed leader in reliability, mobility and energy consumption among the drives of a small and medium capacity, which has good speed and sufficient volume (a flash card to 2 GB is already available on the market). Undoubtedly, this is a very promising type, however, their widespread use is still contained by high prices.
Flash memory is a type of durable memory for computers, in which the contents can be reprogrammed or deleted by the electrical method. Compared to Electrically Erasable Programmable Read Only Memory actions on it can be performed in blocks that are located in different places. Flash memory is much less than EEPROM, so it has become dominant technology. In particular in situations where the sustainable and long-lasting data is required. Its application is allowed in a wide variety of cases: in digital audio players, photo and video cameras, mobile phones and smartphones, where there are special android applications on the memory card. In addition, it is used in USB flash drives traditionally used to save information and its transfer between computers. She received certain fame in the world of gamers, where it often involve in promises for storing data on the progress of the game.
general description
Flash memory is a type that is capable of maintaining information on its board for a long time without using power. In addition, it is possible to note the highest speed of data access, as well as better resistance to kinetic shock in comparison with hard drives. It is thanks to this characteristics that it became a tablet for devices that feed on batteries and batteries. Another indisputable advantage is that when flash memory is compressed into a solid card, it is almost impossible to destroy some standard physical ways, so it can withstand boiling water and high pressure.
Low-level data access
A way to access data in flash memory is very different from what is used for conventional species. Low-level access is carried out by means of a driver. The usual RAM immediately responds to the calls for reading information and its recording, returning the results of such operations, and the flash memory device is such that it will take time to reflections.
Device and principle of operation
On the this moment The flash memory is widespread, which is created on monolayer elements that have a "floating" shutter. Due to this, it is possible to provide greater storage density in comparison with dynamic RAM, which requires a pair of transistors and a condenser element. At the moment, the market is replete with a variety of technologies for the construction of basic elements for this type of media, which are developed by leading manufacturers. It features their number of layers, methods for recording and erasing information, as well as the organization of a structure that is usually indicated in the title.
Currently there are a pair of chip types that are common most: NOR and NAND. In both, the connection of storage transistors is made to the discharge tires - in parallel and consistently respectively. At the first type, the sizes of cells are quite large, and it is possible for quick arbitrary access, which allows programs directly from memory. The second is characterized by smaller cell sizes, as well as rapid consistent access, which is much more convenient if you need to build block-type devices, where large volume information will be stored.
Most portable devices solid State Drive Uses NOR memory type. However, now more popular with USB interface devices are becoming increasingly. They use the NAND type memory. Gradually, she displaces the first.
Main problem - DISTRIBUTY
The first samples of serial production flash drives did not please the users with high speeds. However, now the write speed and reading speed is at such a level that you can view a full-length movie or run on the computer operating system. A number of manufacturers have already demonstrated the machine where the hard drive is replaced by flash memory. But this technology has a very significant disadvantage that becomes an obstacle to replace the existing magnetic disks. Due to the features of the flash memory device, it allows you to produce erase and write information a limited number of cycles, which is achievable even for small and portable devices, not to mention how often it is done on computers. If you use this type of carrier as a solid-state drive on a PC, then a critical situation will come very quickly.
This is due to the fact that such a drive is built on the property of field transistors to maintain in the "floating" shutter The absence or the presence of which in the transistor is considered as a logical unit or zero in binary recording and erasing of the data in the NAND-memory by means of tunneled electrons by Fowler-Nordhaima With the participation of the dielectric. For this it is not required that allows you to make cells of minimal sizes. But just this process It leads to cells, since the electric current in this case causes electrons to penetrate the shutter, overcoming the dielectric barrier. However, the guaranteed period of storage of such memory is ten years. The chip wear occurs not due to reading information, but due to operations for erasing and recording, since reading does not require changes the structure of the cells, but only passes the electrical current.
Naturally, memory manufacturers lead active work in the direction of increasing the service life of solid-state drives this type: They are fixed to ensure the uniformity of the recording / erasing processes on the cells of the array so that some no longer wear out more than others. For uniform load distribution, software paths are predominantly used. For example, the technology of "wear equalization" is used to eliminate such a phenomenon. In this case, the data that is frequently subjected to changes is moved to the address space of the flash memory, therefore the recording is carried out in different physical addresses. Each controller is equipped with its own algorithm of alignment, so it is very difficult to compare the effectiveness of certain models, as the details of the implementation are not disclosed. Because every year the volumes of flash drives are becoming more and more, it is necessary to apply increasingly efficient work algorithms that allow you to ensure the stability of the functioning of devices.
Elimination of problems
One of the very effective ways to combat the specified phenval was the reservation of a certain amount of memory, due to which the load uniformity is ensured and error correction is provided by means of special logical forwarding algorithms for the substitution of physical blocks arising from intensive work with a flash drive. And to prevent the loss of information, the cells that have failed are blocked or replaced with the backup. Such a software distribution of blocks makes it possible to ensure the uniformity of the load, increasing the number of cycles of 3-5 times, however, and this is not enough.
And other types of similar drives are characterized by the fact that the table is entered into their service area file system. It prevents information reads on a logical level, for example, with incorrect shutdown or with a sudden cessation of electrical energy supply. And since when using interchangeable devices, the system does not provide caching, then frequent rewriting has the most detrimental impact on the table of placement of the files and the reference of the catalogs. And even special programs For memory cards are not able to help in this situation. For example, with a single handle, the user rewrote a thousand files. And, it would seem, only one time applied blocks where they are placed. But the service areas corresponded to each of the updates of any file, that is, the placement tables passed this procedure a thousand times. For the indicated reason, first of all, blocks occupied by these data will fail. The technology of "wear equalization" works with such blocks, but its effectiveness is very limited. And it does not matter what your computer you use, the flash drive fails exactly when it is provided by the creator.
It is worth noting that the increase in the capacity of the microcircuit similar devices He led only to the fact that the total number of recording cycles decreased, since cells are becoming less and less, therefore, less and less and voltage is required to dissipate oxide partitions that areolating the "floating shutter". And then the situation develops so that with an increase in the capacity of the devices used, the problem of their reliability began to exacerbate the stronger, and the Class memory card now depends on many factors. The reliability of such a decision is determined by its technical characteristics, as well as the situation in the market currently established. Due to tough competition, manufacturers are forced to reduce the cost of production by any means. Including due to the simplification of the design, the use of components from a cheaper set, weakened the control of manufacturing and other ways. For example, the Samsung memory card will cost more than less known analogs, but its reliability causes much less questions. But it is also difficult to talk about the complete absence of problems, and it is difficult to expect something more unknown producers from devices of completely unknown manufacturers.
Development prospects
If there is obvious advantages whole line The disadvantages that are characterized by an SD memory card that impede the further expansion of its application area. That is why there are constant searches for alternative solutions in this field. Of course, first of all try to improve the existing types of flash memory, which will not lead to some fundamental changes in the existing production process. Therefore, you should not doubt only one thing: firms engaged in the manufacture of these types of drives will try to use all their potential before switching to another type by continuing to improve traditional technology. For example, map sony's memory It is currently produced in a wide range of volumes, so it is assumed that it will continue to actively sold out.
However, today on the threshold of industrial implementation, there is a whole range of alternative data storage technologies, some of which can be implemented immediately upon the occurrence of a favorable market situation.
Ferroelectric RAM (FRAM)
The technology of the Ferroelectric Storage Principle of Information (Ferroelectric Ram, FRAM) is proposed in order to build the potential of non-volatile memory. It is believed that the mechanism of operation of existing technologies, which consists in overwriting data in the process of readings with all modifications of basic components, leads to a certain containment of the high-speed potential of devices. And FRAM is the memory characterized by simplicity, high reliability and speed in operation. These properties are now characteristic of DRAM - non-volatile random access memoryexisting at the moment. But then the opportunity will also be added long storage data, which is characterized by among the advantages of such technology, you can allocate resistance to different types penetrating radiation, which may be requested in special devices, which are used to work in conditions of increased radioactivity or in space research. The storage mechanism here is implemented through the use of a ferroelectric effect. It implies that the material is able to maintain polarization in the absence of an external electric field. Each FRAM memory cell is formed by placing an ultra-hot film from a ferroelectric material in the form of crystals between a pair of flat metal electrodes forming a capacitor. Data in this case is stored within the crystal structure. And this prevents the effect of the charge leakage, which causes the loss of information. The data in the FRAM memory is saved even when the supply voltage is disconnected.
Magnetic RAM (MRAM)
Another type of memory, which today is considered very promising, is MRAM. It is characterized by rather high high-speed indicators and non-volatility. In this case, a thin magnetic film is placed on a silicon substrate. MRAM is a static memory. It does not need periodic overwriting, and the information will not be lost when the power is turned off. At the moment, most of the specialists converge that this type of memory can be called the following generation technology, since the existing prototype demonstrates quite high speed indicators. Another advantage of such a solution is the low cost of chips. Flash memory is manufactured in accordance with the specialized CMOS process. And MRAM microcircuits can be made according to the standard technological process. Moreover, materials can serve as those used in conventional magnetic media. Make large batches of similar chips are much cheaper than everyone else. An important property of MRAM memory is the possibility of instant inclusion. And this is especially valuable for mobile devices. After all, in this type, the cell value is determined by a magnetic charge, and not electrical, as in the traditional flash memory.
OVONIC UNIFIED MEMORY (OUM)
Another type of memory over which many companies are actively working, is a solid-state drive based on amorphous semiconductors. It is based on the phase transition technology, which is similar to the principle of recording on ordinary discs. Here the phase state of the substance in the electric field is changing from crystalline to amorphous. And this change is preserved in the absence of voltage. From traditional optical disks Such devices feature that the heating occurs due to the operation of the electric current, and not a laser. Read in this case is carried out due to the difference in the reflective ability of the substance in various states, which is perceived by the drive sensor. Theoretically, this solution has a high data storage density and maximum reliability, as well as increased speed. High here is the maximum number of overwriting cycles, for which the computer is used, the flash drive in this case lags behind several orders of magnitude.
CHALCOGENIDE RAM (CRAM) and PHASE CHANGE MEMORY (PRAM)
This technology is also based on when in the same phase, the substance used in the carrier acts as a non-conductive amorphous material, and in the second serves as a crystalline conductor. The transition of a storage cell from one state to another is carried out at the expense of electric fields and heating. Such chips are characterized by resistance to ionizing radiation.
Information-Multilayered Imprinted Card (Info-Mica)
The operation of devices built on the basis of such technology is carried out on the principle of thin-film holography. Information is written as follows: First, a two-dimensional image is formed transmitted to the hologram using CGH technology. The data reading occurs due to the fixation of the laser beam on the edge of one of the recorded layers that serve as optical waveguides. The light spreads along the axis, which is placed parallel to the layer plane, forming the image at the output, corresponding to the information recorded earlier. The initial data can be obtained at any time due to the reverse coding algorithm.
This type of memory is relatively different from the semiconductor due to the fact that it provides a high recording density, small power consumption, as well as the low cost of carrier, environmental safety and protected from unauthorized use. But overwrite information such a memory card does not allow, so it can only serve as a long-term storage, replacing paper carrier or alternative optical discs To distribute multimedia content.