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Signaling processors belong to the class of specialized ÌP. They are developed for the solution of tasks of digital processing of signals, the examples of which are:
− filtration of signal;
− folding of two signals;
− calculation of values of cross-correlation function of two signals;
− calculation of autocorrelation function;
− direct-reverse transformation of Fourier’s integrals and others like that.
The tasks of digital processing are solved in the communication equipment and data transfer, tools of hydro- and radio-locations, medical equipment and robotics, engines control, in motor-car electronics, television, in the measuring technique and others like that.
The excellent feature of tasks of digital processing of signals is streaming character of processing of data large volumes in the real mode of time. Operation in real-time requires the increase of ÌP operating speed, and treatment of data large arrays − hardware tools of intensive exchange with peripheral devices.
High operating speed of signaling ÌP is arrived due to:
− to application of modified RISC-architecture;
− to the problem-oriented set of instructions, for example, to plugging in the set of instructions of such operations, as a multiplication with the accumulation of the MAC (Ñ: = ÀõÂ + Ñ) with the marked number of implementations in a command in the cicle and with the rule of change of element indexes of arrays A and B;
− application of reduction methods of command cycle duration, for example conveyorization of commands;
− to placing of operands of most commands in registers;
− to the use of shadow registers for maintenance of the state of calculations during the context switching;
− to the presence of hardware multiplication which enables to execute the multiplication of two numbers for one command clock;
− to hardware support of programmatic cycles.
The signaling processors of different firms-producers are divided into two classes of processors: on the simple and cheap microprocessors of data processing in a format fixedpoint and on expensive microprocessors, that hardwarely support operations above data in a format with a floating comma.
Signaling fixedpoint processors. The first signaling processor ÒÌS320Ñ10, worked out by a firm "Òåõàs ²nstruments" in 1982, processed fixedpoint numbers.
A processor is executed after Harvard architecture basis of which is distribution of access busses to built-in memory of the programs and data. It enables to carry out the selection of command and data in one computer cicle and provide implementation of most commands for one cycle.
The signaling processor ÒÌS320ÕÑ5õ consists of center processor (ÑÐ), built-in memory of the programs and data, multifunction peripheral units, that in most cases enable delivered from an additional external apparatus.
Signaling processors with a floating comma. The use of signaling processors for data processing in a format with floating point is predetermined by the row of tasks (integral transformations, algorithms of compression, decompression, adaptive filtration) which require high exactness of data presentation in a wide dynamic range. Operation with data in a format with a floating point simplifies and accelerates their processing, promotes program reliability, as does not require implementation of operations of rounding off and normalization of data, from hunting of situations of underflow and overflow. However hardware and cost expenses of such ÌP considerably more, than processors of data processing in a format with a fixedpoint.
The first representative of class of processors with a floating comma was ÌP of ÒÌS320Ñ30.
A processor has a 32-bit bus of commands and data and 24-bit bus of address, contains 2 blocks of RAM in 1Ê of 32-bit words, 32-bit block of multiplication with a floating comma, cache memory of commands by a capacity 64, that has a 32-bit words, 8 registers for operations with the increased exactness, 2 generators of address and register file, will realize the different addressing modes. 40-bit ALD of processor operates both with integers and with numbers in a format with a floating comma. Built-in controller DMA enables to connect in time a calculation and exchange of data with memory. Presence in ÌP of ÒÌS320Ñ30 of multiprocessor interface, two external interfaces and two serial ports, extended interrupt system simplifies constructing of the systems on its basis.
All operations in a processor are executed for one clock. A processor can in parallel execute in one clock the operation of multiplication and àrithmetic-logic operation with numbers in a format with the fixed or floating comma. A processor has a flexible set of instructions and support of HLL of Ñ.
5.4. BASIC CONCEPTS AND TASKS OF NEURON CALCULATORS
The examples of tasks solution were considered in previous parts, which are well formalized, id est mathematical models are created for them and there can be the applied algorithms which are based on rules of type "if A, then B". However there are tasks, which it is difficult to formalize, id est find the clear algorithm of solution. To such tasks belong :
− pattern recognition, for example, recognition of hand-whritten and printed characters during optical introduction into computer, recognition of blood cell types, recognition of language. Thus an object which is recognized is the data array, which needs to be attributed to one of the known classes a priori;
− clusterization of data (search of regularity). Input data it follows to attribute to any group (cluster) after proper to them "proximity", thus the number of clusters is unknown a priori. As criteria of "proximity" can be used distance between the data vectors, value of correlation factor and others like that;
− approximation of functions. To find a function which approximates unknown, for example set of experimental data. This task is actual during the design of the difficult systems and creation of control system by difficult dynamic objects, for a robust control;
− prognostication. After previous behavior of function, to forecast its behavior in the future. This task is actual for the systems control with forecasting and for the systems of making decision;
− optimization. Aim of these tasks − to find the optimal value of target function which satisfies to the row of limitations.
It should be noted that a man solves well tasks which it is difficult to formalize − recognizes an image, classifies data, forecasts and others like that. Therefore the idea of creation of artificial intellect became actual enough. However for this purpose it was needed to conduct numerous researches of principles of functioning of man brain from the point of view of information processing.
A brain of man is most difficult from the known systems of information processing. There are about 100 milliards of nerve cells in it, or neurons, each of which on the average has 10 000 connections.
Neuron is the special type of cells, basic purpose of which consists in an operative control by organism.
The schematic image of neuron is given on fig. 5.6.
A neuron has a body (soma) 2, tree of inputs (dendrites) 1 and outputs (axons) 4. Dendrites are ramified strongly, penetrating into comparatively large space round a neuron. The initial segment of axon − is thickened axon hump 3, which adjacent to the cell body.
With moving away from cell it gradually narrows and a myelin sheath appears on it which has high electric resistance. On sonm and dendrites an endings of axons take place which go from other nervous cells. Each such ending 5 has the shape of bulge, which is Fig. 5.6. Schematic image of neuron called a synaptic terminal, or synapse. The input signals of dendritic tree (postsynaptic potentials) weighted and summarized on a path to a axon bulge, where an output pulse is generated. Its presence (or intensity) is the function of the weighted sum of input signals. An output signal passes on the branches of axon and arrives to synapses which connect axons with the dendrite trees of other neurons. Through synapses a signal is transformed into a new input signal for adjacent neurons. This input signal can be positive and negative (excitative or brake) depending on the type of synapses. The value of output signal which is generated by synapse can differ from the value of signal which enters synapse. These divergences determine efficiency, or weight of synapse. Synapse weight can change in the process of synapse functioning.
The scientists of different specialities did attempts to create the mathematical model of neuron. Yes, biologists tried to get analytical conception of neuron, that would take into account all its known functional bihavior. However the basic task − information transfer by nervous impulse − was lost among the great number of parameters which belong to physics of pulses conductivity. Therefore tried to replace physical description of neuron by logical. Thus a nervous cell was examined as element which passes information. In 1943 the scientists-mathematicians Ìàê-Êàëëîõ and Ï³òñ represented a neuron as simple switching element which can be in one of two stable states "On" or "Off". A neuron triggers, if the algebraic sum of inputs is more than threshold in this time. A neuron in such presentation can be used as the computer element and enables to build a network of neurons with corresponding thresholds and connections, that would realize an arbitrary boole function or truth table. These researches resulted in the numerous inventions of charts of information proceding, recognizers and sensory analyzers.
Presently mostly use the model of neuron, represented on fig. 5.7.
A neuron has n single-direction inputs (synapses), united with outputs of other neurons and output y (axon), by which a signal (excitation or braking) acts on synapses of next neurons. Synapse is characterized by the value of synaptic connection, or scales wi, that by physical sense is equivalent to electric conductivity. Every neuron is Fig. 5.7. Model of neuron characterized by the running state s by analogy fromby the nervous cells of brain, which can be excited or braked.
Running state of neuron depends on the value of its inputs, weight and, possibly, the previous state. Mostly the state of neuron is determined or as the weighted sum of its inputs
s = (5.1)
or as distance between the input vector and vector of input weights
x = (5.2)
A neuron output y is the function of its state;
y = f(x) (5.3)
The function f (s) is called the function of activating.
The most widespread functions of activating is a step threshold, linear threshold, sigmoid, linear and Gaussian, resulted in a table. 5.1.
Table 5. 1. Functions of activating of neuron
A neuron network is created as a result of association of output neurons with other inputs, thus neurons create layers, united between themselves.
Neuron network is a network with the eventual number of layers which consist of the same elements and different types of connections between the layers of neurons.
Thus the amount of neurons in layers is choosen on principle of ensuring of the set quality of task solution, and amount of neuron layers − as possible less for diminishing of solution duration.
The simplest single-layer neuron network which is yet called simple perseptron is represented on fig. 5.8, a. Signals come to n inputs, which pass along synapsis to three neurons which form an only layer with output signals
where j = 1…3.
Double-layer perseptron, got from the single-layer by addition of second layer which consists of two neurons, is represented on fig. 5.8, b. Thus non-linearity of activating function matters very much: if it was not, result of functioning of any p - layer of neuron network with the gravimetric matrices W(³) = 1,2,..p for every layer and would be taken to multiplying of input vector of signals X by the matrix of W(S) = W(1)*W(1)*W(2) *.*W(ð), id est actually such p - layer neuron network would be equivalent single-layer with the gravimetric matrix of only layer W(S) : Y = Õ W(S).
Fig.5.8. Single- (a) and double-layer (b) perseptrons
Except the number of layers and connections between them, neuron networks are classified as acyclic or cyclic. Shown on a fig. 5.8, a, b examples belong to the acyclic neuron networks. The example of cyclic neuron network is represented Fig. 5.9. Cyclic neuron network on fig. 5.9.
If supplement considered charts (see fig. 5.8 and 5.9) by condition about clocking of network (to set duration of neurons trigger), then we will get a hardware for assignment of different algorithms for the data processing by means of neuron networks, which can be used for solution of both the formalized tasks and tasks which it is difficult to formalize. In the last case application of neuron networks is based not on implementation of the offered algorithm, but on memorizing by network of given to it examples on the stage of networking and making of results, coordinated with these examples, on the stage of task solution.
Under the type of signals a neuron networks are divided into binary (digital) and analog. The digital networks operate binary signals, and the output of every neuron can take only two values − 0 or 1. After possibility of adaptation it is possible to mark out: neuron networks which construct and teach. In networks which construct, they set a number and type of neurons, graphs of transneuronal connections, weight of inputs, and in networks which teach, − graphs of transneuronal connections and weight of inputs which are changed during implementation of learning algorithm.
After the learning algorithm the networks are divided into a network, which are under supervision, are not under supervision and mixed (hybrid). The first in the process of studies compare a priori known result with got. The second study, not knowing the correct values of result. They group input data so that they formed the same output of network. Such approach is used, for example during the task solution of clusterization. At the mixed learning algorithm the part of weight is determined during a supervision, and part − without a supervision.
PART 6. PERIPHERAL DEVICES
6.1. EXTERNAL MEMORY − MAGNETIC and OPTICAL DISK DRIVES, FLASH MEMORY
A disk drive (FDD - Floppy Disk Drive) is a carrier of data, that operates with variable magnetic disks. Floppy magnetic disks (discettes) enable to carry documents and programs from one computer into other, to keep information which is not used in a computer constantly, and do archival copy.
In the personal computers two types of disk drives are used − for a diskette of size 3,5 inch (89 mm) and for a diskette by the size of 5,25 inch (out-of-date model).
In modern computers they use stores for diskettes of size 3,5 inch by a capacity 1,44 Ìbyte.
Diskettes are celled in a hard plastic envelope, that considerably increase their reliability and longevity. There is special switch-latch on diskettes, that allows or forbids to conduct a record on a diskette.
Let us consider descriptions of this data carrier.
Capacity. Presently the capacity of diskette 1,44 MByte dissatisfy users. According to modern necessities on software products, that have ten and hundreds megabyte, on such data medium it is possible to carry the small volumes of data only.
Reliability. Comparatively with other data mediums the mechanism of diskette is unreliable enough, as mechanics of disk drive is such, that a headduring work touches magnetic surface, damaging it. In addition, a disk surface is badly protected from influence of surroundingenvirounmentand has electromagnetic instability.
Operating speed. A read/record rate at the use of diskettes presents about 30 ÷ 50 Kb/s comparatively with 20 ÷ 40 Mb/s at a hard disk. Thus, suchoperating speed extremely unsatisfactory, in consideration of small capacity of carrier.
Price. The cost of disk drive and diskettes is relatively small and, as a result, high availability of users to it as a carrier of data.
Popularity. In spite of that a disk drive is actively used relatively a long ago, it and presently most widespread in the modern personal computers.Many solutions were offered, that tried to force out a disk drive, however deciding this task was not succeeded.To this time such technology of storage of information did not have at the market a competition which would provide more subzero cost of store and data carriers.In addition, obvious advantage is possibility of record which enables to carry information from one computer on other.
The computer-integrated on a system board controller of disk drive (FDC - Floppy Disk Controller) enables to plug in two disk drives.
For pluging of disk drives they apply the special cable which has 34 conductor. A device number is determined on a cable, as two disconnectors of cable unidentical. A device which is connected to the end of cable gets a number 1, and a device which is connected to the middle of cable is a number 2.
For the task solution of providing of greater capacity on one variable carrier (diskette) with acceptable operating speed comparatively with a general disk drive a company IOmega created a store which was named by IOmega Zip 100 Ìb.
In this store a diskettes of capacity100 Mb are used, thus for it it is impossible to insert ordinary diskettes, but only special diameter 3,5 inches and in thick about 9 mm.
Instead of Zip100 began to produce the new model − Zip250 Ìb, that operates as with diskettes 250 Mb, so with diskettes 100 Mb. This store operates practically with any interface: IDE, LPT, USB. Basic advantages are − simplicity of setting and exploitation and not-difficult software, proper operating speed. However operating speed belongs only to the internal models or models with interface USB, a device with the interface LPT is limited to the productivity of parallel port oneself. Basic defects are − repugnance with ordinary diskettes and not very much high reliability of device.
Flash-memory. Lately flash-memory is used not only as internal memory but also as external, that connected to the computer through the interface USB. Such device can be switched on and off without the restart of computer. A device has: microcircuits of flash -memory, controller which manages access to the microcircuits, adapter USB.
Devices have small sizes, different forms of corps, that manufactured from a plastic or aluminium. During access to them an indicator lights up. Permission or prohibition of read-out is realized by a switch with the use of password. A device can be used as loadable. Basic properties of external storage such: appropriate capacity (16, 32, 64, 128, 256, 512 Mb or 1, 2, 4 Gb), speed of data transfer, reliability.
Maximal speed of data transfer for devices reaches 1,5 Mb/s (USB 1.1) and 50,60 Mb/s for USB 2.0. Duration of data retention about 10 years, the amount of rewriting cycles reaches 1 million.
Flash-memory is used not only in computers, but in mobile telephones, network equipment, printers, faxes and others like that. Microcircuits are produced by all producers of memory microcircuits.Suchmicrocircuitshave built-in electric circuits which enable to generate adischarg for erase of data or on all microcircuit, or on some its areas − blocks and provide access to data of short duration.
In some devices it is possible connection of flash-disk, player with reiteration functions, digital dictaphone and FÌ-radio.
So, a basic problem is providing of adequate tools of delivery and distribution of information. Carriers must contain the enormous volumes of different information, allow fast access to some its components, their high-quality recreation, and here to be cheap, compact and reliable. This problem was solved after appearance of optical disks of different types.
Presently there are three types of technology of optical memory. The first type − it is a disk drive ROM on a compact disk (ÑD - RÎÌ) named so because it uses optical disks according to sample optical disks in stereo sound systems, and functionally corresponds to the permanent memory. The second type − disk drive WORM (Write Once, Read Ìany times) a record is possible only one time, but reading of data is frequent. The third type has many names − optical with rewriting, optical with erase of information, magnetically-optical.
ÑD - RÎÌ (Ñompact Disk Read Înly Ìåmîãó) − optical disk, which consists of thin aluminium tape, covered by the protective layer of polymer.Record of information on ÑD - RÎÌ takes place during its making,by means ofpunching, as a result in an aluminium layer a picture is created from hollows due to which the code of information is carried out.At the read-out of ÑD in the special device which is called by ÑD - RÎÌ - Drive, the surface of aluminium is scanned by a laser ray, and then laser light is analysed, reflected from the surface of disk, whereupon the picture of hollows on a disk is restored and thus written information is read.
ÑD - RÎÌ − round disk by diameter 120 mm with the central opening by diameter 15 mm, thickness 1,2 mm. The central area round opening by a width 6 mm is called a fastening area (clamping area). After it directly there is title part(lead in area)which contains maintenance of disk (table of content). After title part the area is placed in a width a 33 mm, intended for storage of data. Physically it is only track. Finishing is a terminal area(lead out)in a width a 1 mm. External dinner of disk has a width a 3 mm.
ÑD – RÎÌ are made by the method of punching. At first make plastic basis from the transparent plastic or polycarbonate, whereupon over a plastic for the reflection of laser ray they spread the layer of aluminium, which, in turn, is covered by the protective layer of varnish.One can see this argenteum well from the back of transparent disk.
The area of data storage contains from 1 to 99 tracks usually, but placing different information on one track is not allowed. Digit information is saved on ÑD - RÎÌ as microscopic hollows − pits, which are alternated downstep of spiral.
Typical length of pit presents 0,8 ÷ 3,2 μm, width − 0,6, depth − 0,12, and distance between the separate paths − 1,6 μm. On one inch (2,54 cm) of disk surface 16 thousand or 625 turns take place on one millimetre (for comparison on one inch of magnetic disk 96 paths are contained only). Due to such small values of pits a ÑD - RÎÌ contains the enormous volume of information − about 700 Mb. The new types of disks have on an order a greater volume and feasible record of information by an user. The read-out of ÑD is carried out in a special device which is called by ÑD - ROM - Drive.
It is known that most stores are external and built-in (internal). Most stores of offered presently ÑD - ROM are built-in.
On the front panel of every store there is access to the mechanism of loading of compact disk. One of most widespread there is a mechanism of ÑD - ROM loading by means of caddy − plastic container in which they lay a compact disk before loading direct in a drive. Another way of loading − by means of tray-mechanism, which similar to the tray which is pulled out from a store usually after pressure of the button "Åject". On it they set a compact disk, whereupon they push tray-mechanism in a store by hand. There are varieties of tray-mechanism, for example ðîð-uð. In this case loading of disk is semi-automatic and place is taken after an easy touch.
In addition, on the front panel of drive it is placed: indicator of device operation (busy), nest for connecting of earphones or stereo sound system (for listening of audiodisks), automatic fader (also for àóä³îCD). For the system of ñàddy the opening is foreseen also by means of which it is possible to fish out a compact disk even in an emergency situation, for example, if the button of "Åject" malfunctions.
On the backplane of almost all drivers of ÑD - RÎÌ there are usually three disconnectors: interface, feed and audio. In particular, a disconnector for the leadingout of voice signals enables to connect a driver to a sound card.
Except these disconnectors in case of the use of SCSI-interface there is a set of jumpers or switches on the backplane of drive which
Fig. 6.1. Typical device of store CD-ROM Drive
determine a device number and its operation mode.
Typical device of store ÑD-RÎÌ Drive is represented on fig. 6.1. In the drive of compact disks there are a few base elements
- laser diode, servomotor, optical system, photodetector.
Operating principle of disk drive is similar to operating principle of ordinary disk drives for floppy disks.
Semiconductor laser 4 generates a low-powered laser ray which gets on reflecting mirror.
Motor, controlled by microprocessor ÑD-RÎÌ Drive displaces a movable carriage 6 with a mirror and lens 7 to the necessary path of compact disk 1. The ray of laser focuses on the surface of ÑD-RÎÌ by means of lens which focuses a reflected from the surface of disk ray. This ray by means of the optical system 5 is delivered on a detector 2, which converts the accepted light pulses into electric, which are then decoded by a controller 3 and transfered to the computer as digital data.
So, the read-out of information from a disk takes place due to login of intensity change of reflected emission from the aluminium layer of low-powered laser. If a ray gets in pit, it disperses, and only small part of emission is reflected back and comes to the photosensitive diode. On a diode light impulses transform in electric, in particular, bright emission is converted into zero, and weak − into unit. Thus, pits are interpreted by a disk drive as logical zeros, and smooth surface − as logical units.
The surface of optical disk (ÑD-RÎÌ) moves relatively lazer head with permanent linear speed (ÑLV, Ñîïstant Linear Velocity), and an angular speed changes depending on radial position of head. Yes, reading of internal sectors is carried out with accelerated, and external − with the diminished number of turns. That is why a speed of access to CD data is less than, for example, with winchesters.
Basic properties of ÑD-RÎÌ, as data storage, are such.
Productivity of almost any device of data storage it is possible to describe by two major parameters − duration of access and speed of linear read-out. Duration of access is determined by rotation speed of compact disk and by the rate of movement of read-out head. Speed of access (àññåss time) determines mean time (ms), necessary for an exposure and loading of the first block of data in an internal buffer. The standard of ÌÐÑ1 sets such time −1s or less than, but most modern drives have speed of access 50 ÷ 80 ms. Clearly, that this parameter does not include time, necessary for the running of motor at operating condition.
Speed of datatransfer (dats-transfer rate) depends on two factors − data density and speed of disk rotation. The data density – it is the amount of bits (pits) on an inch (or millimetre). Yes, for 16-bit stereosignal of quality àudio-ÑD (frequency 44,1 kHz) speed must be 1,4 Ìb/s. Dividing this value by the number of bits in a byte (8), will get 176,4 Kb/s − mean value for data transfer speed. Standard ÌÑÐ 1 determines data transfer speed 150 Kb/s. Producers measure read-out speed of ÑD-RÎÌ Drive by numbers, multiple to this minimum speed. For example, if speech goes about the four-speed device of read-out of disks (4õ), then it means that such ÑD-RÎÌ Drive can provide speed of read-out from a disk 150 Kb/s ∙ 4 = 600 Kb/s. Presently mostly use disks with speeds of 40õ ÷ 50õ.
Reliability. It is known that at first ÑD developed for storage of music records. If at the recreation of music from a compact disk the incorrect read-out of one bit will take place, then it in any way will not influence on quality of recreation. Therefore on disks with the music records it is provided less of measures in relation for providing of read-out reliability. If a disk is processed with data, then an incorrect read-out even of one bit will result in complete uselessness of finding. Therefore on a disk with data, except useful information, they write down surplus (superfluous) data by means of which in case of uncertain reading of any information content it is possible to restore it. Yes, on ÑD there are very powerful codes of error correction, which enable to restore about 1000 (!) bits which unright go in succession. For example, if on a disk is written music, then size of block of 2352 bytes fully used forstorage of musical data, and if the data written on a disk, then only a 2048 byte is used actually for data storage, and other 304 bytes are used for official necessities, in particular a 288 byte for the special redundant code of error correction.
Except such programmatic defence which presents the about 1/6 useful capacities of disk, a disk is protected yet by polymeric tape. On the whole ÑD can be considered the reliable enough carrier of data, but it needs the enough careful use: it follows to protect a disk surface from scratches and mechanical damages.
Size of buffer. For the increase of the disk drives productivity they are supplied with buffer memory. A buffer of disk drive is memory for data short-term storage after the read-out of them from ÑD-RÎÌ, but yet before transfer in controller. Such buffering enables to the disk device to pass data to the processor by small portions, but not to occupy its time by the slow transfer of permanent data flow. The standard ÌÐÑ sets the buffer size 64 Kb, and it in a buffer will be about 0,4 s of 16-bit stereosignal as ÑD-Àudio with frequency 44,1 kHz. For speed devices the size of buffer can reach 256 Kb and even 1 Mb.
Capacity and price. Comparatively with a diskette, a compact disk has a considerably higher capacity: 650 Mb. Such capacity predetermines application of compact disk as a data carrier for different installative distributive packages for storage of which before applied diskettes. It is assisted by the subzero cost of ÑD-RÎÌ Drive, which presently is inalienable component of any PC and subzero cost of carrier ÑD-RÎÌ.
Devices for a record on ÑD. Devices which enable to conduct a record on laser disks name ÑD-R Drive (ÑD Recordable), and disk which a record is done on, − ÑD-R. Clean ÑD-R has not a single deepening on the surface. During a record on the disk surface the laser ray of recoder burns out deepening, realizing thus record of information. Clearly, that, writing down information on such disk, it can not be erased or changed. Speed of devices is usually marked by two numbers, for example 4õ/24õ, id est record is carried out on speed 4õ, and a read-out − on 24õ.
Except ÑD-R with a single record there are devices for a frequent record and erase of information − ÑD-RW (ÑD RåWritable). Disk ÑD-RW has an active layer of the alloy Àg − ²n − Sb − Te. Layer of such alloy at heating to 500 ÷ 700 °Ñ is melted, losing a reflection property, and it is thus possible to record a new information. After heating to the temperature about 200 °Ñ property of layer are restored, thus, record on such carrier it is possible to do repeatedly. Accordingly, devices for a record on ÑD-RW can yet write down the gold disks ÑD-R and to read ordinary ÑD-RÎÌ. Device is marked by three speeds, for example, 4õ/10õ/32õ, that means rewrite on speed 4õ, record on ÑD-R on speed 10õ, read-out on speed 32õ. ÑD-RW have large prospects. Yes, at the acceptable price of device, it is, at first, good device for information storage, and, secondly, − universal method of information transfer.
DVD - discs. The future of compact disks − is a digital universal disk, so-called DVD (Digital Versatile Disc). It is a new standard which increases the volume of memory considerably. Main problem of modern technology of ÑD-RÎÌ consists in that it is hardly limited by the size of disk memory. Disk ÑD-RÎÌ can contain 650 Mb of data maximally, and although it is a very large volume, butit is not enough to solve many tasks, especially for those, which use video.
Specification of DVD. In accordance with the standard DVD-disk is a single-sided, single-layer and contains 4,7 Gb of information.
A new disk has the same diameter, as modern compact disks, but it is twice more thin (0,6 mm). DVD-disks keep data also in a shape of microscopic deepening, minimum length of which presents 0,4 μm. In addition, a spiral path in the disks of DVD has a step of 0,74 μm. For the read-out of information from DVD a red laser is used of lengh wave 635 ÷ 650 nm. Diminishing of sizes of deepening and step of spiral path assisted the increase of disks capacity of almost seven times.
Applying a compression by the standard ÌÐÅG - 2, on a new disk it is possible to place 135 min video, id est a full-length film is with the complete amount of frames, with three channels of high-quality sound and four channels of sub-title. The value of disk capacity is not random, as it was created for the use in film industry which required inexpensive and reliable replacement of video cassettes a long ago. In a store DVD a laser is used with a less wave-length, which enables to read considerably short strokes.
Most disks of DVD have a capacity 4,7 Gb. Application of doubling density charts and their combining, enables to have disks of greater capacity: from 8,5 and 9,4 Gb to 17 Gb. Such structural types of DVD are known.
Single Side/Single Layer: it is a simplest structure of DVD-disk. On such disk it is possible to place to 4,7 Gb of data, in particular this capacity more than capacity of ordinary sound ÑD and ÑD-RÎÌ-disks in 7 times.
Single Side /Dual Layer: this type of disks has two layers of data, one of which semitransparent. Both layers are readen from one side and on such disk it is possible to place 8,5 Gb of data, id est on 3,5 Gb more than on the sigle-sided/single-layer disk.
Double Side/Single Layer: on such disk 9,4 Gb of data (for 4,7 Gb on every side) are placed.
Double Side/Double Layer: structure of this disk provides possibility to place to 17 Gb of data (for 8,5 Gb on every side) on it.
Nine companies which presently lead in development of new generations of DVD-technologies, − Í³tàñh³, LG Ålectronics, Ìàtsushita Ålåñtã³ñ, Ð³înååã Ñîrðîãàt³în, Rîóàl Ðh³l³ðs Ålåñtãîn³ñs, Sàmsung Ålåñtãîn³ñs, Shàrp Ñîrðîràt³în, Sînó and Òhîmsîn Ìult³måd³à announced the new format of recoding of optical disks for video.
This format has the name "Âlu-ràó D³sñ". The name of technology was given after length by the laser radiations − blue-violet, which will apply during work with new disks. New disks of standard of Âlu-ràó D³sñ, as well as present ÑD/DVD carriers, have a diameter 120 mm. Disks of Âlu-ràó enable to write down on every side about 50 Gb of data at the use of laser with the wave-length of 405 nm. Yes, a firm Òîshiba produced bilateral DVD of capacity 110 Gb.
It should be noted that the devices of DVD differ in read-out speed of data. Standard speed − is 1,3 Mb/s, that approximately equivalence to the store of ÑD-RÎÌ 9õ. Duration of access equals about 100 ÷ 150 ms. Presently there are stores DVD 16õ. Such carriers fully pin-compatible with previous standard, can read-out data from ordinary ÑD-RÎÌ and to play back audiodisks.
Connecting of ÑD-RÎÌ, ÑD-R, ÑD-RW, DVD-RÎÌ. All enumerated devices connect like a hard disk. They keep up the same modes of Ð²Î 1,2,3,4, UDMA 33,66,100.
Lately most widespread are SÑS² and IDÅ interfaces. In turn, both interfaces SÑS² and IDÅ have the improved versions. For SÑS² − this SÑS² - 2 and Fast SÑS² - 2, for IDE there is interface of EIDE.
There are a few methods of connecting of disk drives of ÑD-RÎÌ. The first method is based on that one channel of interface IDE can keep up two built-in devices. Store ÑD-RÎÌ connect to the input-output board through the interface IDE together with hard disk by principle master/slave. However in this case speed of data exchange goes down with a hard disk. One of methods of this problem solving there is connecting of devices ÑD-RÎÌ to the different channels of one interface ÅIDE or to two different contrpllers IDE. For connecting of these devices apply the same 40-pin (40-or 80-conductor) cables.
If ÑD-RÎÌ has SÑS² interface, then it accordingly plug in to SÑS² of controller. Other approach is application of 32-bit drivers of disk drives ÑD-RÎÌ instead of 16-bit. There is also possibility of connecting of disk drives ÑD-RÎÌ through controller of sound card. However one cannot to forget that modern system boards can contain the built-in controllers SÑS² and IDE, that in general eliminates a requirement in the additional input-output board for connecting of disk drives ÑD-RÎÌ.
6.2. VIDEO SYSTEMS − MONITORS, VIDEO CARDS, DEVICES of VIDEO DATA PROCESSING
Basic units of the video system of PC there are a monitor and video card. Monitor, or display, − device for information representationon on the screen of computer. Exactly through a monitor all visual information is perceived from a computer. A health and first of all sight of operator depend on quality and safety of monitor.
Computer monitors in the process of operation use three base colors: red (R), green (G), blue (B) (fig. 6.2). For their denotation apply abbreviation RGB. A monitor with the complete range of colors will have 256 gradations of every primary color, id est it can recreate 256 õ 256 õ 256 = 16 700 000 colors (such monitor is called "fullcoloured").
In modern PC use three basic types of monitors: ÑRÒ (Ñathode Ray Òèbå) − monitors with cathode or electron-ray tubes; LCD (L³quid Ñrystal Dispiay); ÐDÐ (Ðlàsmà Dispiay Ðàïål).
A major element of ÑRÒ - monitor is kinescope (fig. 6.3) which is yet called an electron-ray tube (ERT). A kinescope consists of Fig. 6.2. Distribution of primary vacuum hermetic glass colours on computer monitor tube. One of ends of tube narrow and long − it is a mouth, and other − wide and
sufficiently flat − it is a screen. From a frontal side the inside part of glass tube is covered by luminophor – substance, which radiates the light under its borbadment by charged particles.
Fig. 6.3. Kinescope: (1 − glass; 2 − luminophor coverage; 3 – fastener; 4 – clamp)
For creation of image in coloured ÑRÒ-monitor they use three electron guns, from where three electron flows go out accordingly. Every gun answers one of primary colors and produces the beam of electrons under the action of the strong electrostatic field. On a path to the forehand of tube the flows of electrons pass through the intensity modulator and system of acceleration, where they get considerable enough energy, a part of which is spent on luminescence of luminophor.
Distinguish ERT with the delta-shaped and planar placing of electron guns. ERT with the planar placing name also tubes with erection of rays, as action of magnetic-field of Earth on the planar placed ray is almost identical, that is why in case of tube position change relative to the field of Earth it is not needed to do its additional adjustings.
The brightness of certain color is determined by intensity which falls on that or other point of ray. For the correction of electron beams (that they got on the necessary point of luminofor) use a special mask. Through a metallic mask or grates the electron beams get on the internal surface of glass screen of monitor, which is covered by varicoloured luminophor points. Thus they get on the different particles of luminophor, which shine primary colors with different intensity and as a result an image is formed with a neccesary color.
It is needed for the receipt of the high-quality coloured image, that ray, intended for red luminophor elements, not influences on the luminophor of green or blue color and vice versa. As electron guns are on certain distance one from other, then the angles of arrival of electron beams differ insignificantly, that enables create mask so that a necessary ray got on the corresponding point of luminophor, and other rays were closed by a mask. In the kinescopes certain types of masks are used (fig. 6.4).
Shadow mask.In this Fig. 6.4. Types of masks in monitors: a − ERT with a shadow mask; b − ERT with aperture grates; 1 − mask; 2 − luminophors; 3÷5 − accordingly green, red and blue rays; 6 − strings
technology the coloured element consists of three grains, placed in the tops of correct triangle. The sharpness of image is determined by distance between the geometric centers of neighbours of elements. A shadow mask consists of metallic net (usually from the alloy of iron and nickel) before part of glass tube with luminophor layer. This net provides hit of electrons on certain luminophor element. Minimum distance between the luminophor elements of identical color is called dot ð³tch, which is the important parameter of image quality. The dot pitch is measured in millimetres. The less value of dot pitch, the higher quality of the recreated image. So, in the model of Í³tàñh³ ÑÌ77² the step of shadow mask presents a 0,22 mm for horizontals and 0,14 mm − for vertical lines.
Slot Mask.Luminophor elements are placed in vertical elliptic cells, and a mask is made out of verticals. Minimum distance between two cells is called a slot pitch. A slot mask is applied in monitorscompany NÅÑ (under the name "Ñrîmà Ñlåàr") and monitors of firm Ðànàsîn³ñ with the tube Ðurå Flat. A firm LG in the monitors uses the flat slot tube Flàtrîn with a step 0,24 mm.
Àðårture Grillcontain the series of strings, that consist of luminophor elements, built as vertical stripes of three primary colors. Such system provides the high contrasty of image and proper saturation of colors. Mask which is set in tubes of firm Sony (Ì³tsubishi, View Sonic), is thin foil which vertical thin lines are plotted on. Basic advantage of this technology it is the saturated colors gamma. In addition, screen in monitors is less convex, than in monitors with shadow slot masks.
The electron flow can deviate in vertical and horizontal planes, that provides a successive its hit on all field of screen. The beam deflection takes place due to deflector system.
Every pixel which is used for the generation of image in a point has certain co-ordinates on the plane of monitor screen. It is however impossible to compare the size of step in the tubes of different types. So, the step of points in tubes with a shadow mask is measured bias, while step of the aperture grate − on horizontals. Therefore at the identical step of points a tube with a shadow mask has a less density of points, than tube with an aperture grate. For example, step a 0,25 mm in an aperture grate almost equivalent to 0,27 mm − in a shadow.
Operational principle of LCD-monitors (Liquid Ñrystal D³sðlàó) is based on the polarization phenomenon of light flow. Screens of monitors are made of a substance which is in the liquid state and has properties, typical for crystalline bodies. The molecules of liquid crystals (Liquid Ñrystal) can change the orientation under the action of electrons, owing to properties of light ray change also, that passes through them.
LCD - monitorhas a few layers, where a basic role is carried out by two panels(they are made of very clean glass material which sodium is withdrawn from),that contain a thin layer of liquid crystals between themselves. On panels there are grooves which send crystals, giving a special orientation to them. Grooves are placed so, that they are parallel on every panel, but perpendicular between two panels.Longitudinal gooves appear as a result of placing on the glass surface of thin tapes of transparent plastic which is then processed. Impacting with gooves, molecules in liquid crystals are oriented identically in all cells.
Turn of polarization plane of light ray is unnoticeable for the eye, that is why there was a necessity to add to the glass panels two other layers which are polarization filters. So, filters transmit a that light beam, which polarization axis answers set only. Therefore at passing of polarizator a light beam will be weak depending on a angle between its polarization plane and axis of polarizator.
In default of voltage a cell is transparent, as the first polarizator skips only light with the corresponding vector of polarization. Due to liquid crystals the vector of light polarization returns, and to the moment of beam passing to second polarizator it is already returned so, that passes through second polarizator without obstacles (fig. 6.5, à).
At presence of electric field the turn of polarization vector occures on a less angle, that is why second polarizator becomes only partly transparent for a radiation. If potentials difference will be such, that the turn of polarization plane does not take place in liquid crystals, then the light ray is consumed by the second polarizator, and screen at illumination Fig. 6.5. Operation principle of LCD-monitor behind or at the front without voltage (a) and under voltage it will seem black (fig. 6.5, b)
Thus, a screen of LCD-monitor is an array of little cells − segments (pixels), by which it is possible to manipulate for displaying of information. For the leadingout of color display it is necessary lighting from behind of monitor so that light go out of the back-end of LCD-display. It is needed in order to look an image with the proper quality, even if environment pale.
As well as in traditional ERT tubes the pixel LCD-monitor is formed from three primary colors − RGB. A color appears as a result of use of three filters, which distinguish from a radiation of white light source a three basic components and value changes of certain electrical charge which causes the turn of crystal and change of brightness of corresponding light flow. Combining three primary colors for every point or pixel of screen, possibility of recreation of any color appears.
There are a few types of LCD-monitors:
STN (Super Twisted Nematic) − technology of STN enables to increase the torsion angle(twisting angle)of crystals orientation inside LCD-display from 90 to 270°, that provides the best contrasty of image in thecase of monitor size increase;
DSTN (dual-scan twisted nematic) − crystalline screens with dual-scan. In this construction one double-layer DSTN-cell consists of two STN-cells, the molecules of which during operation turn into opposite sides.Light, passing through such construction in the "closed" state, loses greater part of the energy. A contrasty anddiscrimination are high enough, that is why possibility to make a colour display in which on every pixel are due three cells and three optical filters of primary colors appeared.
ÒFÒ (thin film transistor) − monitors on thin-film transistors.The thin-film transistor(thick 0,1÷0,01 μm)− it the controlled elements by means of whichevery pixel is controlled on the screen. Apixel on the basis of ÒFÒ is arranged so: in a glass plate after each other three coloured filters RGB are placed. Every pixelis combination of three color cells or subpixel elements. ÒFÒ-screen consists of whole net of such pixels, where operation of certain color area of every pixel is controlled by a separate transistor, forexample, in a display which has discrimination of 1280 õ 1024, there are 3840 õ 1024 transistors and subpixel elements. The size of point (pixel) for a 15,1" display ÒFÒ (1024 õ 768)approximately presents 0,0188 inch (or 0,30 mm), and for 18,1" display ÒFÒ − about 0,011 inch (or 0,28 mm).
S - ÒFÒ − monitors Sèðår ÒFÒ. In technology S-ÒFÒ use simple metallic electrodes, set on a bottom glass plate, which forcesmolecules to be revolved, which constantly are in plane, parallel to screen plane. Therefore an image on a display remains bright and clear even at the large viewing angle, arriving quality which is compared to the image on a ERT-screen.
Basic properties and differences of LCD-monitors. Real diagonal size of screen. The visible diagonal size of ERÒ-monitor always less, than actual diagonal size of tube, as losses after the scope of monitor present close inch. In ÒFÒ-panel this area is not, so a diagonal size is such, that and visible diagonal. Thus, panel by a size 15,1" is equivalent to size 17" of ERÒ-monitor. All the PC have standard monitors − 15 or 17". For professional work with graphic material use monitors of size 19, 21 or 22".
The contrasty ratio is determined of the values of maximal and minimum values of brightness. On ÑRÒ-monitors this ratio presents 500:1, that enables to get photo-realistic quality of picture. For LCD this ratio has a far fewer value. Itespecially notedly during displaying of black color. On ERÒ-monitor a black is formed simply enough − by the change of level of all colour constituents.For displaying of black a liquid crystals must fully block passing of light. However physically it not possibly and light partly passes through crystals. Presentlyacceptable values for LCD are 250:1 ÷ 300:1.
Brightness. The maximal brightness of TFT-displays is determined by possibilities of backlight lamp. Therefore to createbrightness of200 ÷ 250 cnd/m2is not problem, although in practice there is not a necessity. Maximal brightness of ERÒ-monitor presents 100 ÷ 120 cnd/m2. Creating the greater value of brightness is possible, but it negatively will influence on the operation term of luminophors. Presently brightness in ÒFÒ - and ERÒ-monitors almost identical.
Viewing angle. This property is critical almost for all flat-panel displays. The maximal viewing angle equals to an extreme value at which the contrast ratio goes down to 10:1 from the defined value in case of perpendicular position to the screen plane. The serious lack of LCD-monitors is a viewing angle: even in the last models not always it is possible normally to see an image, if to look at a monitor under an angle. However this problem begins to solve: if before a viewing angle for LCD-monitor was about 45°, then presently there are models with the viewing angle to 170°.
Discrimination. Modern monitors provide minimal discrimination of 800 õ 600 pixels. Maximal discrimination it is possible to define in ÑRÒ-monitor, dividing the visible size of screen by the step of point, slot step or step of stripe. Yes, maximal discriminationof monitor by a size 17" with a slot mask, by the step of points 0,25 mm and by the screen size 320 õ 240 mm presents 1478 õ1109 pixels. It should be noted that ÑRÒ-monitors during operation can use different values of discrimination in the full-screen mode, while LCD-monitors − only one. A less discriminationis possible for them in case of the use of part of screen. So, on a monitor with the discrimination 1024 õ 768 at the discrimination 640 õ 480 will be used only 66 % of screen. Application of the special functions of "overscan" on all screen results in the considerable diminishing of the clearness and distortion of image.
Inertia. Duration of transfer of pixel from one state in other is called an inertia. ÑRÒ-monitors have the least value of inertia − 10 ms. For LCD-monitors it is one of critical properties, that resulted in a visible delay in the process of displaying of animation plots. For modern ÒFÒ-displays the value of inertia presents 20 ÷ 30 ms. For example, for the normal revision of video it is neededto display 25 frames by 1 s, id est every frame can be reflected no more than 40 ms. Thus, ÒFÒ-displays assist the revision of videoplots on the whole.
Refresh rate. Frequency of reiteration of frames is called refresh rate. The eye of man see change of images as the movable image then, when frequency of image change not below, than 20 ÷ 25 Hz. However for operation with a monitor at a short distance to screenit is not enough of such frequencies, as the higher frequency of frames, the more steady image. For ÑRÒ-monitorsduration of glow of luminophor elements is small enough, that is why an electronic ray must pass through every element of luminophor layer often enough, that the noticeable twinkling of image was not. Iffrequency of screen bypass less, than 70 Hz, then to the inertia of visual perception it will be not enough in order to getunwinking image, that is why minimum safefrequencyof frames is considered75 Hz. Twinkling of image (flicker)resuins in the fatigue of eyes, headache and even to the visual impairment. The brightness of separate element of screen of LCD-monitorremains not-variable during all time between renewals of the pictures. The greater screen of monitor, the more noticeable twinkling, especiallyby peripheral (lateral) sight, as a visual angle of image increases. During work with LCD-monitor loading on eyes considerably less, id est the even plane ofscreenand absence of twinkling is designated. It is the lack of LCD-monitors, as a frequent change of emage, for example duringviewingof films, influences on the inertia of pixels switching from one state into other, thatresults in distortion of image. Refresh rateof LCD-monitors not below, than 20÷50 Hz, that is why for implementation of the multimedia applied tasks it is better to use ÑRÒ-monitors.
Beam convergence. In LCD-monitors every pixel is placed in the fixed matrix and switched separately, that is why there are no problems withbeam convergence, unlike ÑRÒ-monitors, where it is needed faultless operation of electron guns. Thus LCD-monitors provide the ideal clearness of image. So, the picture of 17-inch ÒFÒ-monitor at the discrimination of 1280 õ 1024 excels in a clearnessan image even of 19-inch ÑRÒ-monitor, for which such mode is considered optimal.
Electromagnetic radiation. Variable electromagnetic fields which are created by the power module and all electric chart, in LCD-monitor radiates the same as ÑRÒ-monitor. However LCD-monitor has a zero permanent potential of display, id est does not create round itselffar more harmful permanent electrostatic potential.
Efficiency. LCD-monitor has power 15 ÷ 30 W, whereas 17-inch ÑRÒ-monitor − 80÷130 W.
Overall dimension. LCD-monitors does not have a kinescope, instead of them compact LCD-matrix is used, that is why it is possible to make maximally compact monitors. If in ordinary ÑRÒ –monitor a thickness equals to the screen diagonal approximately, then liquid-crystal monitors thin enough, their thickness reaches 5÷10 cm. For example, one 15-inch ÑRÒ-monitor weighs 15 kg, and LCD-monitor in thick a 15 cm together with support − less than 6 kg
Absence of reflexes. Refleciton factor of light from the surface of LCD-monitor in three and more times less, than from the surface of kinescope with the most perfect presently coverage of antireflection − Sony FD Trinitron, Mitsubishi Diamondtron NF.
Front-end interface. By the method of transfer of signals between a video card and monitor distinguish digital and analog monitors. In digit monitors the color signal of RGB is passed in the discrete(digital)state by a separate conductor. Analog monitors operate with the video cards of standards VGA, SVGA and other They are capableto keep up discrimination of 640x480 pixels and anymore. In these monitors a signal is passed as a result of voltage change. An analog interface is used in all modern ÑRÒ-monitors, there is a digital interface DVI (Digital Visual Interface) in LCD-monitorsand plasma monitors. However majority of LCD-monitors have built-in analog interface for connecting to the most widespread analog outputss of video adapters. The interface of DVI foreseespossibility of transfer, except digital data, analog signals in ÑRÒ-monitors.
Pixel errors. There are "dead points" on some LCD-monitors. It takes place as a resultof transistor defects, id est a certaintransistor can not control a light flow. It always blocks light, or always skips it. According to a standard,a presence to five "dead pixels" on new LCD-monitor is assumed.
Turn of screen. It should be noted and such feature of some LCD-monitors, as possibility of screen turn on 90° with the simultaneous automatic turn of image. So, presently the sheet of format À4can be fully placed on the screen, without a necessity to use thevertical scrolling to see all text on a page.
Operation principle of ÐDÐ (Ðlasma Display Panel)of plasma monitors (fig. 6.6) consists in theguided cold discharging of rarefied gas which is in theionized state (cold plasma).Plasma screens make,filling space between two surfaces, by rare gas, for example by an argon or neon. By a operating element (pixel) which forms a certain point of image, there is a group of three subpixels. Every subpixel – it is separate micro-camera on the walls of which there isa fluorescence substance of one of basic colors. Pixels are in cross points of transparent electrodes which create a rectangular net.
In order that luminescence of pixel took place a controlled variable voltage of rectangular form is given at two ortogonal to each other electrodes in the point of which crossing there is a necessary pixel. Under its action in a gaseous medium an electric discharge arises which radiates light in an ultraviolet range, which predetermines luminescence of luminophor particles in