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91-554: The MCS-48 series has a modified Harvard architecture , with internal or external program ROM and 64 to 256 bytes of internal (on-chip) RAM . The I/O is mapped into its own address space , separate from programs and data. Though the MCS-48 series was eventually replaced by the very successful MCS-51 series, it remained quite popular even by the year 2000 due to its low cost, wide availability, memory-efficient one-byte instruction set, and mature development tools. Because of this, it

182-494: A Betamax video recorder in 1973. After this, in 1974 the leap to storing digital audio on an optical disc was easily made. Sony first publicly demonstrated an optical digital audio disc in September 1976. A year later, in September 1977, Sony showed the press a 30 cm (12 in) disc that could play 60 minutes of digital audio (44,100 Hz sampling rate and 16-bit resolution) using MFM modulation. In September 1978,

273-592: A DJ mixer to transition seamlessly between songs. In the 1970s disco era, DJs typically used two record players . From the 1980s to the 1990s, two compact cassette players became a popular sound source for DJs. In subsequent decades, DJs shifted to CDs and then to digital audio players . DJs who use CDs and CD players typically use specialized DJ CD players that have features not available on regular CD players. DJs who are performing scratching –the creation of rhythmic sounds and sound effects from sound recordings–traditionally used vinyl records and turntables . In

364-614: A headphone jack or RCA jacks . To use a CD player in a home stereo system, the user connects an RCA cable from the RCA jacks to a hi-fi (or other amplifier ) and loudspeakers for listening to music. To listen to music using a CD player with a headphone output jack, the user plugs headphones or earphones into the headphone jack. Modern units can play audio formats other than the original CD PCM audio coding, such as MP3 , AAC and WMA . DJs playing dance music at clubs often use specialized players with an adjustable playback speed to alter

455-428: A photodiode array sensor. The sensor detects changes in the beam, and a digital processing chain interprets these changes as binary data. The data are processed and eventually converted to sound using a digital-to-analog converter (DAC). A TOC or Table of Contents is located after the lead-in area of the disc, which is located in an inner ring of the disc, and contains roughly five kilobytes of available space. It

546-500: A CD player. The boombox CD player is the only type of CD player that produces sound audible by the listener independently, without the need for headphones or an additional amplifier or speaker system. Designed for portability, boomboxes can be powered by batteries as well as by line current. The boombox was introduced to the American market during the mid-1970s. The desire for louder and heavier bass led to bigger and heavier boxes; by

637-584: A Mini CD inserted will refuse to operate until such disc is removed, for example). Non-circular CDs cannot be used on such loaders because they cannot handle non-circular discs. When inserted, such discs may become stuck and damage the mechanism. It is also used on some laptop computers, the original and slim PlayStation 3 , the Wii's original model and its Family Edition and most eighth-generation video game consoles (the Wii U , PlayStation 4 and Xbox One ), as well as

728-448: A characteristic eye pattern and its usefulness in servicing the machine is paramount for detecting and diagnosing problems, and calibrating CD players for operation. The first stage in the processing chain for the analog RF signal (from the photoreceptor device) is digitizing it. Using various circuits like a simple comparator or a data slicer, the analog signal becomes a chain of two binary digital values, 1 and 0. This signal carries all

819-422: A magnetic actuator mounted on a swing-arm to do coarse and fine tracking. Using only one laser beam and the 4 photodiode block, the servo knows if the track is centered by measuring side-by-side movement of the light of beam hitting on the block and corrects to keep the light on the center. The other design by Sony uses a diffraction grating to part the laser light into one main beam and two sub-beams. When focused,

910-471: A mechanism that scans the circular data tracks using a laser beam. An electric motor spins the disc. The tracking control is done by analog servo amplifiers and then the high-frequency analog signal read from the disc is digitized, processed and decoded into analog audio and digital control data which is used by the player to position the playback mechanism on the correct track, do the skip and seek functions and display track, time, index and, on newer players in

1001-509: A million copies on CD was Dire Straits , with their 1985 album Brothers in Arms . The first major artist to have his entire catalogue converted to CD was David Bowie , whose 15 studio albums were made available by RCA Records in February 1985, along with four greatest hits albums. In 1988, 400 million CDs were manufactured by 50 pressing plants around the world. The CD was planned to be

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1092-462: A modification. A picture of this early design can be seen on the Panasonic Web site. The vertical loading is similar the one common in cassette decks , where the holder opens, and disc is dropped to it. The holder is closed manually, by motor after pressing a button, or completely automatically. Some CD players combine vertical loading with slot loading due to the disc being drawn further into

1183-469: A modified Harvard ARM9 core, necessarily provides uniform access to flash memory and SRAM (as 8 bit bytes, in those cases). Outside of applications where a cacheless DSP or microcontroller is required, most modern processors have a CPU cache which partitions instruction and data. There are also processors which are Harvard machines by the most rigorous definition (that program and data memory occupy different address spaces), and are only modified in

1274-523: A pair of headphones . The first portable CD player released was the D-50 by Sony . The D-50 was made available on the market in 1984, and adopted for Sony's entire portable CD player line. In 1998, portable MP3 players began to compete with portable CD players. After Apple Computer entered the music player market with its iPod line, within ten years it became the dominant seller of portable digital audio players, "...while former giant Sony (maker of

1365-427: A pure von Neumann architecture is that – when executing an instruction from one memory segment – the same memory segment cannot be simultaneously accessed as data. Three characteristics may be used to distinguish modified Harvard machines from pure Harvard and von Neumann machines: For pure Harvard machines, there is an address "zero" in instruction space that refers to an instruction storage location and

1456-473: A result, in 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc. Led by engineers Kees Schouhamer Immink and Toshitada Doi , the research pushed forward laser and optical disc technology. After a year of experimentation and discussion, the task force produced the Red Book CD-DA standard. First published in 1980, the standard was formally adopted by

1547-686: A separate address "zero" in data space that refers to a distinct data storage location. By contrast, von Neumann and split-cache modified Harvard machines store both instructions and data in a single address space, so address "zero" refers to only one location and whether the binary pattern in that location is interpreted as an instruction or data is defined by how the program is written. However, just like pure Harvard machines, instruction-memory-as-data modified Harvard machines have separate address spaces, so have separate addresses "zero" for instruction and data space, so this does not distinguish that type of modified Harvard machines from pure Harvard machines. This

1638-670: A team." Red Book was the first standard in the Rainbow Books series of standards. Philips established the Polydor Pressing Operations plant in Langenhagen near Hannover , Germany , and quickly passed a series of milestones. The Japanese launch was followed in March 1983 by the introduction of CD players and discs to Europe and North America (where CBS Records released sixteen titles). This event

1729-604: A unified access path covers the rest of the memory hierarchy . A von Neumann processor has only that unified access path. From a programmer's point of view, a modified Harvard processor in which instruction and data memories share an address space is usually treated as a von Neumann machine until cache coherency becomes an issue, as with self-modifying code and program loading. This can be confusing, but such issues are usually visible only to systems programmers and integrators . Other modified Harvard machines are like pure Harvard machines in this regard. The original Harvard machine,

1820-552: A year of experimentation and discussion, the Red Book CD-DA standard was published in 1980. After their commercial release in 1982, compact discs and their players were extremely popular. Despite costing up to $ 1,000, over 400,000 CD players were sold in the United States between 1983 and 1984. The success of the compact disc has been credited to the cooperation between Philips and Sony , who came together to agree upon and develop compatible hardware. The unified design of

1911-466: Is self-modifying code , which allows a program to modify itself. A disadvantage of these methods are issues with executable space protection , which increase the risks from malware and software defects. Accordingly, some pure Harvard machines are specialty products. Most modern computers instead implement a modified Harvard architecture. Those modifications are various ways to loosen the strict separation between code and data, while still supporting

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2002-539: Is a DVD player/boombox with a top-loading CD/ DVD drive and an LCD video screen in the position once occupied by a cassette deck. Many models of this type of boombox include inputs for external video (such as television broadcasts) and outputs to connect the DVD player to a full-sized television. Disc jockeys (DJs) who are playing a mix of songs at a dance club , rave , or nightclub create their dance mixes by having songs playing on two or more sound sources and using

2093-547: Is a variation of the Harvard computer architecture that, unlike the pure Harvard architecture, allows memory that contains instructions to be accessed as data. Most modern computers that are documented as Harvard architecture are, in fact, modified Harvard architecture. The original Harvard architecture computer, the Harvard Mark I , employed entirely separate memory systems to store instructions and data. The CPU fetched

2184-556: Is also necessary to know the memory space (instruction or data) to which the address belongs. A computer with a von Neumann architecture has the advantage over Harvard machines as described above in that code can also be accessed and treated the same as data, and vice versa. This allows, for example, data to be read from disk storage into memory and then executed as code, or self-optimizing software systems using technologies such as just-in-time compilation to write machine code into their own memory and then later execute it. Another example

2275-456: Is fed to two systems, one integrated in the focus lens assembly can do fine tracking correction and the other system can move the entire optical assembly side by side to do coarse track jumps. The sum of the output from the four photodiodes makes the RF or high-frequency signal which is an electronic mirror of the pits and lands recorded on the disc. The RF signal, when observed on an oscilloscope, has

2366-409: Is in charge of keeping focused the beam on the 600  nm wide data track. When the player tries to read from a stop, it first does a focus seek program that moves the lens up and down from the surface of the disc until a reflection is detected; when there is a reflection, the servo electronics lock in place keeping the lens in perfect focus while the disc rotates and changes its relative height from

2457-452: Is invalid, erroneous or missing audio data, it cannot be output to the speakers as digital noise, it has to be muted. The Audio CD format requires every player to have enough processing power to decode the CD data; this is normally made by application-specific integrated circuits (ASICs). ASICs do not work by themselves, however; they require a main microcomputer or microcontroller to orchestrate

2548-401: Is not based on Russell's invention; it is an evolution of LaserDisc technology, where a focused laser beam is used that enables the high information density required for high-quality digital audio signals. Prototypes were developed by Philips and Sony independently in the late 1970s. In 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc. After

2639-450: Is often seen as the "Big Bang" of the digital audio revolution. The new audio disc was enthusiastically received, especially in the early-adopting classical music and audiophile communities, and its handling quality received particular praise. As the price of players gradually came down, and with the introduction of the portable Walkman , the CD began to gain popularity in the larger popular and rock music markets. The first artist to sell

2730-437: Is still restricted to the program address space, these processors are very unlike von Neumann machines. External wiring can also convert a strictly Harvard CPU core into a modified Harvard one, for example by simply combining `PSEN#` (program space read) and `RD#` (external data space read) signals externally through an AND gate on an Intel 8051 family microcontroller, the microcontroller are said to be "von Neumann connected," as

2821-414: Is the first information that the player reads when the disc is loaded in the player and contains information on the total number of audio tracks, the running time on the CD, the running time of each track, and other information such as ISRC and the format structure of the disc. The TOC is of such vital importance for the disc that if it is not read correctly by the player, the CD could not be played back. That

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2912-518: Is the point of pure or modified Harvard machines, and why they co-exist with the more flexible and general von Neumann architecture: separate memory pathways to the CPU allow instructions to be fetched and data to be accessed at the same time, improving throughput. The pure Harvard machines have separate pathways with separate address spaces. Split-cache modified Harvard machines have such separate access paths for CPU caches or other tightly coupled memories, but

3003-439: Is the preferred loading mechanism for car audio players. There is no tray that pops out, and a motor is used to assist disc insertion and removal. Some slot-loading mechanisms and changers can load and play back Mini-CDs without the need of an adapter (such as the original Wii model's standard-sized disc slot being capable of accepting smaller GameCube Game Discs ) but they may work with limited functionality (a disc changer with

3094-415: Is used in high-volume, cost-sensitive consumer electronics devices such as TV remotes, computer keyboards, and toys. The 8049 has 2 KB of masked ROM (the 8748 and 8749 had EPROM ) that can be replaced with a 4 KB external ROM, as well as 128  bytes of RAM and 27  I/O ports. The microcontroller's oscillator block divides the clock input frequency by three and then further divides

3185-597: Is why it is repeated three times before the first music program starts. The lead out area in the end (the outer peripheral) of the disc tells the player that disc has come to an end. CD players can employ a number of ways to improve performance or reduce component count or price. Features such as oversampling, one-bit DACs, dual DACs, interpolation (error correction), anti-skip buffering, digital and optical outputs are, or were, likely to be found. Other features improve functionality, such as track programming, random play and repeat, or direct track access. Yet others are related to

3276-585: The IEC as an international standard in 1987, with various amendments becoming part of the standard in 1996. Philips coined the term compact disc in line with another audio product, the Compact Cassette , and contributed the general manufacturing process , based on video LaserDisc technology. Philips also contributed eight-to-fourteen modulation (EFM), which offers a certain resilience to defects such as scratches and fingerprints, while Sony contributed

3367-500: The Mark I , stored instructions on a punched paper tape and data in electro-mechanical counters. This, however, was entirely due to the limitations of technology available at the time. Today a Harvard machine such as the PIC microcontroller might use 12-bit wide flash memory for instructions, and 8-bit wide SRAM for data. In contrast, a von Neumann microcontroller such as an ARM7TDMI , or

3458-427: The error-correction method, CIRC . The Compact Disc Story , told by a former member of the task force, gives background information on the many technical decisions made, including the choice of the sampling frequency, playing time, and disc diameter. The task force consisted of around four to eight persons, though according to Philips, the compact disc was "invented collectively by a large group of people working as

3549-404: The ninth-generation PlayStation 5 and Xbox Series X . Two types of optical tracking mechanisms exist: The swing-arm mechanism has a distinctive advantage over the other in that it does not skip when the rail becomes dirty. The swing arm mechanisms tend to have a much longer life than their radial counterparts. The main difference between the two mechanisms is the way they read the data from

3640-412: The pitch and tempo of the music. Audio engineers using CD players to play music for an event through a sound reinforcement system use professional audio-grade CD players. CD playback functionality is also available on CD-ROM/DVD-ROM drive equipped computers as well as on DVD players and most optical disc-based home video game consoles . American inventor James T. Russell is known for inventing

3731-506: The "separate address space" nature of a Harvard machine, but provides special machine operations to access the contents of the instruction memory as data. Because data is not directly executable as instructions, such machines are not always viewed as "modified" Harvard architecture: A few Harvard architecture processors, such as the Maxim Integrated MAXQ, can execute instructions fetched from any memory segment – unlike

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3822-513: The 1980s, some boomboxes had reached the size of a suitcase . Most boomboxes were battery-operated, leading to extremely heavy, bulky boxes. Most boomboxes from the 2010s typically include a CD player compatible with CD-R and CD-RW , which allows the user to carry their own music compilations on a higher fidelity medium. Many also permit iPod and similar devices to be plugged into them through one or more auxiliary input jacks. Some also support formats such as MP3 and WMA . Another modern variant

3913-411: The 2010s, display title and artist information on a display placed in the front panel. To read the data from the disc, a laser beam shines on the surface of the disc. Surface differences between discs being played, and tiny position differences once loaded, are handled by using a movable lens with a very close focal length to focus the light on the disc. A low-mass lens coupled to an electromagnetic coil

4004-686: The 8042's functions into their super I/O devices. The 8048 was used in the Magnavox Odyssey² video game console , the Korg Trident series, and the Korg Poly-61 , Roland Jupiter-4 and Roland ProMars analog synthesizers . The Sinclair QL used the closely related Intel 8049 to manage its keyboard, joystick ports, RS-232 inputs and audio. The ROM-less 8035 variant was used in Nintendo 's arcade game Donkey Kong to generate

4095-413: The CD player's intended target, such as anti-skip for car and portable CD players, pitch control and queuing for a DJ's CD player, remote and system integration for household players. Description of some features follows: A portable CD player is a portable audio player used to play compact discs . Portable CD players are powered by batteries and they have a 1/8" headphone jack into which the user plugs

4186-649: The PC's Intel 8255 peripheral interface chip at I/O port addresses 0x 60–63 with an 8042 accessible through port addresses 0x60 and 0x64 . As well as managing the keyboard interface, the 8042 controlled the A20 line gating function for the AT's Intel 80286 CPU and could be commanded by software to reset the 80286 (unlike the 80386 and later processors, the 80286 had no way of switching from protected mode back to real mode except by being reset). Later PC compatibles integrate

4277-568: The Philips CD100 chassis. Top-loading was adopted on various equipment designs such as mini systems and portable CD players, but among stereo component CD players, only a handful of top-loading models have been made. Examples include Luxman 's D-500 and D-500X series players and Denon 's DP-S1, both launched in 1993. Top-loading is also common in players intended for broadcast and live sound DJ use, such as Technics' SL-P50 (1984–1985) and Technics SL-P1200 (1986–1992). They more closely mimic

4368-577: The Sony prototype design was never put into volume production, the concept was for a time adopted for production by a number of early Japanese CD player manufacturers, including Alpine/Luxman , Matsushita under the Technics brand, Kenwood and Toshiba/Aurex . For the early vertical loading players, Alpine sourced their AD-7100 player designs for Luxman, Kenwood and Toshiba (using their Aurex brand). Kenwood added their Sigma Drive outputs to this design as

4459-426: The United States. In Japan, however, over 80 percent of music was bought on CDs and other physical formats as of 2015. As of 2020, compact cassettes, vinyl records, and CDs are still being released by some musicians, primarily as merchandise, to allow fans to provide financial support while receiving something tangible in return. The process of playing an audio CD, touted as a digital audio storage medium, starts with

4550-555: The [portable] Walkman and [CD] Discman [was] struggling." This market shift was initiated when the first portable digital audio player, the Rio digital music player , was introduced. The 64 MB Rio MP3 player enabled users to store about 20 songs. One of the benefits of the Rio over portable CD players was that since the Rio had no moving parts, it offered skip-free playback. Since 1998, the price of portable digital audio players has dropped and

4641-543: The advent and popularity of Internet-based distribution of files in lossily-compressed audio formats such as MP3 , sales of CDs began to decline in the 2000s. For example, between 2000 and 2008, despite overall growth in music sales and one anomalous year of increase, major-label CD sales declined overall by 20% – although independent and DIY music sales may be tracking better (according to figures released 30 March 2009), and CDs still continue to sell greatly. As of 2012, CDs and DVDs made up only 34 percent of music sales in

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4732-408: The audio division of Philips , started a small group with the aim to develop an analog optical audio disc with a diameter of 20 cm (7.9 in) and a sound quality superior to that of the vinyl record. However, due to the unsatisfactory performance of the analog format, two Philips research engineers recommended a digital format in March 1974. In 1977, Philips then established a laboratory with

4823-533: The background music. Philips Semiconductors (now NXP ) owned a license to produce this series and developed their MAB8400-family based on this architecture. These were the first microcontrollers with an integrated I²C -interface and were used in the first Philips ( Magnavox in the US) Compact Disc players (e.g. the CD-100). Modified Harvard architecture A modified Harvard architecture

4914-508: The compact disc allowed consumers to purchase any disc or player from any company, and allowed the CD to dominate the at-home music market unchallenged. The Sony CDP-101 , released in 1982, was the world's first commercially released compact disc player. It was originally sold only in Japan. Unlike early LaserDisc players, first CD players already used laser diodes instead of larger helium-neon lasers . In 1974, Lou Ottens, director of

5005-507: The company demonstrated an optical digital audio disc with a 150-minute playing time, 44,056 Hz sampling rate, 16-bit linear resolution, and cross-interleaved error correction code—specifications similar to those later settled upon for the standard compact disc format in 1980. Technical details of Sony's digital audio disc were presented during the 62nd AES Convention, held on 13–16 March 1979, in Brussels . Sony's AES technical paper

5096-457: The correction is made by interpolating the data from subsequent frames so the missing part is not noticed. Each player has a different interpolation ability. If too many data frames are missing or unrecoverable, the audio signal may be impossible to fix by interpolation, so an audio mute flag is raised to mute the DAC to avoid invalid data to be played back. The Redbook standard dictates that, if there

5187-433: The data cache. Most programmers never need to be aware of the fact that the processor core implements a (modified) Harvard architecture, although they benefit from its speed advantages. Only programmers who generate and store instructions into memory need to be aware of issues such as cache coherency , if the store doesn't modify or invalidate a cached copy of the instruction in an instruction cache. Another change preserves

5278-510: The disc holder as it closes. In 1983, Philips , at the US and European launch of the CD format, showcased the first top loading CD tray designs with their CD100 CD player. (Philips audio products were sold as Magnavox in the US at the time.) The design had a clamp on the lid which meant the user had to close this over the CD when it was placed inside the machine. Later, Meridian introduced their MCD high end CD player, with Meridian electronics in

5369-432: The disc. The swing-arm mechanism uses a magnetic coil wound over a permanent magnet to provide the tracking movement to the laser assembly in a similar way a hard drive moves its head across the data tracks. It also uses another magnetic movement mechanism attached to the focusing lens to focus the laser beam on the disc surface. By operating the tracking or the focus actuators, the laser beam can be positioned on any part of

5460-402: The disc. This mechanism employs a single laser beam and a set of four photodiodes to read, focus and keep track of the data coming from the disc. The linear tracking mechanism uses a motor and reduction gears to move the laser assembly radially across the tracks of the disc and it also has a set of six coils mounted in the focusing lens over a permanent magnetic field. One set of two coils moves

5551-600: The early 2000s, the CD player had largely replaced the audio cassette player as standard equipment in new automobiles, with 2010 being the final model year for any car in the US to have a factory-equipped cassette player. Currently, with the increasing popularity of portable digital audio players, such as mobile phones, and solid state music storage, CD players are being phased out of automobiles in favor of minijack auxiliary inputs and connections to USB devices. Some CD players incorporate disc changers. Commonly these can hold 3, 5, 6, or 10 discs at once and change from one disc to

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5642-403: The entire machine. The firmware of basic CD players typically is a real-time operating system . Some early optical computer drives are equipped with an audio connector and buttons for standalone CD playback functionality. Sony released its CDP-101 CD player in 1982 with a slide-out tray design for the CD. As it was easy to manufacture and to use, most CD player manufacturers stayed with

5733-470: The external data and program address spaces become unified. Having separate address spaces creates certain difficulties in programming with high-level languages that do not directly support the notion that tables of read-only data might be in a different address space from normal writable data (and thus need to be read using different instructions). The C programming language can support multiple address spaces either through non-standard extensions or through

5824-405: The first system to record digital video information on an optical transparent foil that is lit from behind by a high-power halogen lamp. Russell's patent application was first filed in 1966, and he was granted a patent in 1970. Following litigation, Sony and Philips licensed Russell's recording patents (then held by a Canadian company, Optical Recording Corp.) in the 1980s. The compact disc

5915-465: The higher performance concurrent data and instruction access of the Harvard architecture. The most common modification builds a memory hierarchy with separate CPU caches for instructions and data at lower levels of the hierarchy. There is a single address space for instructions and data, providing the von Neumann model, but the CPU fetches instructions from the instruction cache and fetches data from

6006-509: The information in a CD and is modulated using a system called EFM (Eight-to-fourteen modulation). The second stage is demodulating the EFM signal into a data frame that contains the audio samples, error correction parity bits, according with the CIRC error correction code, and control data for the player display and micro-computer. The EFM demodulator also decodes part of the CD signal and routes it to

6097-524: The key matrix, converts switch closures to an 8-bit code and then transmits that code serially to the keyboard interface on the main system. It will also accept commands to turn indicator LEDs on or off. The 8021 was also used in the keyboards for the TRS-80 Model 12, 12B, 16, 16B and the Tandy 6000/6000HD. The original IBM PC keyboard used an 8048 as its internal microcontroller . The PC AT replaced

6188-417: The lens closer to the disc surface, providing the focusing motion, and the other set of coils moves the lens radially, providing a finer tracking motion. This mechanism uses the three-beam tracking method in which a main laser beam is used to read and focus the data track of the disc using three or four photodiodes, depending on the focus method, and two smaller beams read the adjacent tracks at each side to help

6279-440: The mission of creating a digital audio disc. The diameter of Philips's prototype compact disc was set at 11.5 cm (4.5 in), the diagonal of an audio cassette. Heitaro Nakajima , who developed an early digital audio recorder within Japan's national public broadcasting organization NHK in 1970, became general manager of Sony 's audio department in 1971. His team developed a digital PCM adaptor audio tape recorder using

6370-519: The next instruction and loaded or stored data simultaneously and independently. This is in contrast to a von Neumann architecture computer, in which both instructions and data are stored in the same memory system and (without the complexity of a CPU cache ) must be accessed in turn. The physical separation of instruction and data memory is sometimes held to be the distinguishing feature of modern Harvard architecture computers. With microcontrollers (entire computer systems integrated onto single chips),

6461-402: The next without user intervention. Disc changers capable of holding up to 400 discs at once were available. Also, the user can manually choose the disc to be played, making it similar to a jukebox . They were often built into car audio and home stereo systems, although 7 disc CD changers were once made by NEC and Nakamichi for PCs. Some could also play DVD and Blu-ray discs. Meanwhile, with

6552-538: The now standardized extensions to support embedded processors . CD player A CD player is an electronic device that plays audio compact discs , which are a digital optical disc data storage format. CD players were first sold to consumers in 1982. CDs typically contain recordings of audio material such as music or audiobooks . CD players may be part of home stereo systems, car audio systems, personal computers , or portable CD players such as CD boomboxes . Most CD players produce an output signal via

6643-425: The optical block. Different brands and models of optical assemblies use different methods of focus detection. On most players, the focus position detection is made using the difference in the current output of a block of four photodiodes. The photodiode block and the optics are arranged in such a way that a perfect focus projects a circular pattern on the block while a far or near focus projects an ellipse differing in

6734-522: The original Harvard processor, which can only execute instructions fetched from the program memory segment. Such processors, like other Harvard architecture processors – and unlike pure von Neumann architecture – can read an instruction and read a data value simultaneously, if they're in separate memory segments, since the processor has (at least) two separate memory segments with independent data buses. The most obvious programmer-visible difference between this kind of modified Harvard architecture and

6825-409: The outside edge. (A disc played from beginning to end slows its rotation rate during playback.) The tracking mechanism moves the lens system along the spiral tracks in which information is encoded, and the lens assembly reads the information using a laser beam produced by a laser diode . The laser reads information by focusing a beam on the CD, which is reflected off the disc's mirrored surface back to

6916-478: The physical arrangement and ergonomics of record turntables used in those applications. The top-loading disc tray design is also used in most fifth-generation video game consoles ( PlayStation , Saturn , 3DO Interactive Multiplayer ), as well as the Dreamcast , GameCube , and Wii Mini . The Philips CD303 of 1983-1984 was the first player to adopt tray loading with a sliding play mechanism. Basically, as

7007-408: The plastic polycarbonate compact disc, a medium that contains the digitally encoded data. The disc is placed in a tray that either opens up (as with portable CD players) or slides out (the norm with in-home CD players, computer disc drives and game consoles). In some systems, the user slides the disc into a slot (e.g., car stereo CD players). Once the disc is loaded into the tray, the data is read out by

7098-423: The position of the long edge in north–south or west-southwest. That difference is the information that the servo amplifier uses to keep the lens at the proper reading distance during the playback operation, even if the disc is warped. Another servo mechanism in the player is in charge of keeping the focused beam centered on the data track. Two optical pick-up designs exist, the original CDM series from Philips use

7189-408: The possibility of serial communication, reducing the amount of conductors needed in cables on external keyboards. Microprocessors had been used in keyboards since at least 1972, simplifying earlier discrete designs. The 8048 has been used in this application since its introduction in 1978. The Tandy/Radio Shack TRS-80 Model II , released in 1979, used the 8021 in its keyboard. The 8021 processor scans

7280-430: The proper circuits, separating audio, parity and control (subcode) data. After demodulating, a CIRC error corrector takes each audio data frame, stores it in a SRAM memory and verifies that it has been read correctly, if it is not, it takes the parity and correction bits and fixes the data, then it moves it out to a DAC to be converted to an analog audio signal. If the data missing is enough to make recovery impossible,

7371-484: The result into five machine states. Using the 11  MHz maximum crystal frequency will produce 0.73  MIPS of single-cycle instructions . Some 70% of instructions are single byte and single cycle ones, but 30% need two cycles or two bytes, so its typical performance would be closer to 0.5 MIPS. The MCS-48 series was commonly used in computer and terminal keyboards, converting key presses into protocols that can be understood by digital circuits. This also allows

7462-416: The servo keep the tracking using two more helper photodiodes . A CD player has three major mechanical components: a drive motor , a lens system or pickup head, and a tracking mechanism . The drive motor (also called spindle) spins the disc to a scanning velocity of 1.2–1.4 m/s ( constant linear velocity ) – equivalent to approximately 500 RPM at the inside of the disc, and approximately 200 RPM at

7553-435: The storage capacity has increased significantly. In the 2000s, users can "carry [their] entire music collection in a [digital audio] player the size of a cigarette package." The 4 GB iPod, for example, holds over 1,000 songs. A boombox is a common term for a portable cassette and AM/FM radio that consists of an amplifier, two or more loudspeakers and a carrying handle. Beginning in the 1990s, boomboxes typically included

7644-424: The successor of the gramophone record for playing music, rather than primarily as a data storage medium, but from its origins as a format for music, its use has grown to encompass other applications. In 1983, following the CD's introduction, Immink and Braat presented the first experiments with erasable compact discs during the 73rd AES Convention. In June 1985, the computer-readable CD-ROM (read-only memory)

7735-488: The tray came out to collect the CD, the entire player's transport system also came out as one unit. The Meridians 200 and 203 players were of this type. They were also the first to use a design in which the audio electronics were in a separate enclosure from the CD drive and pickup mechanism. A similar mechanism is used in slim optical disc drives (also known as slim internal DVD drive, optical drive or DVD burner), which were once commonly used in laptop computers. Slot loading

7826-548: The tray style ever since. The tray mechanism is also used in many modern desktop computer cases , as well as the Philips CD-i , PlayStation 2 , Xbox and Xbox 360 . However, there have been some notable exceptions to this common CD tray design. During the launch of the first prototype Goronta CD player by Sony at the Japanese Audio Fair in 1982, Sony showcased the vertical loading design. Although

7917-428: The two peripheral beams cover the border of the adjacent tracks a few micrometers apart from the main beam and reflect back on two photodiodes separated from the main block of four. The servo detects the RF signal being received on the peripheral receivers and the difference in output between these two diodes conform the tracking error signal that the system uses to keep the optics in the proper track. The tracking signal

8008-399: The use of different memory technologies for instructions (e.g. flash memory ) and data (typically read/write memory ) in von Neumann machines is becoming popular. The true distinction of a Harvard machine is that instruction and data memory occupy different address spaces . In other words, a memory address does not uniquely identify a storage location (as it does in a von Neumann machine); it

8099-529: The weak sense that there are operations to read and/or write program memory as data. For example, LPM (Load Program Memory) and SPM (Store Program Memory) instructions in the Atmel AVR implement such a modification. Similar solutions are found in other microcontrollers such as the PIC and Z8Encore! , many families of digital signal processors such as the TI C55x cores , and more. Because instruction execution

8190-508: Was introduced and, in 1990, the CD-Recordable , also developed by both Sony and Philips. Recordable CDs were a new alternative to tape for recording music and copying music albums without the defects introduced in the compression used in other digital recording methods. Other newer video formats such as DVD and Blu-ray use the same physical geometry as CD, and most DVD and Blu-ray players are backward compatible with audio CD. By

8281-486: Was published on 1 March 1979. A week later, on 8 March, Philips publicly demonstrated a prototype of an optical digital audio disc at a press conference called "Philips Introduce Compact Disc" in Eindhoven , Netherlands . Sony executive Norio Ohga , later CEO and chairman of Sony, and Heitaro Nakajima were convinced of the format's commercial potential and pushed further development despite widespread skepticism. As

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