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Topic: Run Length Limited

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	Run Length Limited - Wikipedia, the free encyclopedia
		Run Length Limited codes, or RLL codes are widely used in hard disk drives (and notably digital optical discs, such as CD, DVD and BluRay disc) to prevent long stretches of no transitions, and therefore decoding uncertainty, from creeping in.
		The length of time (usually expressed in channel bits) between consecutive transitions 0 to 1 or 1 to 0 is known as the runlength.
		Run length limited sequences are characterized by two parameters, (d+1) and (k+1), which stipulate the minimum (with the exception of the very first and last runlength) and maximum runlength, respectively, that may occur in the sequence.
	en.wikipedia.org /wiki/Run_Length_Limited (416 words)

	Run Length Limited (RLL)
		The two parameters that define RLL are the run length and the run limit (and hence the name).
		The run length is the minimum spacing between flux reversals, and the run limit is the maximum spacing between them.
		The particular variety of RLL used on a drive is expressed as "RLL (X,Y)" or "X,Y RLL" where X is the run length and Y is the run limit.
	www.storagereview.com /guide2000/ref/hdd/geom/dataRLL.html (711 words)

	Run length limited encoding/decoding system for low power disk drives - Patent 5349350
		The run length limited encoding/decoding system of claim 7 wherein said serializer circuit means further comprises a plurality of parallel output terminals wherein said plurality of output terminals are operatively connected to said encoding logic circuit means.
		The run length limited encoding/decoding system of claim 8 wherein said serializer circuit means is a second shift register having n bits and further wherein said second shift register is different from said first mentioned shift register.
		A novel run length limited encoding/decoding system that minimizes propagation delays and the associated timing jitter problems includes a deserializer means, operatively coupled to a serial data stream from a disk drive controller, for blocking the serial data steam into m bit data words.
	www.freepatentsonline.com /5349350.html (12040 words)

	RLL - Run Length Limited
		RLL produces fast data access times and increases a disk's storage capacity over the older encoding scheme called MFM (modified frequency modulation).
		Run Length Limited: a method used on some hard disks to encode data into magnetic pulses.
		The 'run length' is the number of consecutive 0s before a 1 bit is recorded.
	www.auditmypc.com /acronym/RLL.asp (306 words)

	Apparatus and method for increasing density of run length limited block codes without increasing error propagation - ...
		For example, starting with an RLL code having a coding density of 8/9 (I=8, J=9) and constraint set of (0,4,4), inserting one uncoded byte between each coded byte (M=1) results in a coding density of 16/17 which is 5.88% greater than the original 8/9 coding density.
		Run length limited block codes intended for use in hard disk drives typically have a coding density of I/J, where I is an integer number which is ordinarily an integer multiple or submultiple of 8, and J is a larger integer.
		Run length limited block codes intended for use in hard disk drives typically have a coding density of I/J, where I is the symbol length of the outer error correction code which is typically 8 bits, and J is a larger integer.
	www.freepatentsonline.com /5604497.html (3430 words)

	Partitioned DC balanced (0,6) 16B/18B transmission code with error correction - Patent 6198413
		The method of claim 39, further comprising the step of limiting a running disparity in the succession of coded vectors by tracking the running disparity at boundaries between the alternating coded vectors based on the succession of coded vectors with a disparity of zero, plus two, minus two, plus four, or minus four.
		The "run length" (RL) is the maximum number of contiguous one or zero bits, either inside bytes or across byte boundaries, as seen on the transmission media, i.e., after an NRZI operation, if applicable.
		The singular comma may generate a run length of two followed by a run length of seven and ending with a run length of one in the ten-bit domain, followed by a run length of three in the 8B domain.
	www.freepatentsonline.com /6198413.html (14723 words)

	Micro House PC Hardware Library Volume I: Hard Disks: Hard Disk Drives
		In RLL encoding, groups of bits are taken as a unit and combined to generate specific patterns of flux reversals.
		The term Run Length Limited is derived from the two primary specifications of these codes, which is the minimum number (the run length) and maximum number (the run limit) of transition cells allowed between two actual flux transitions.
		RLL 2,7 initially was the most popular RLL variation because it offers a high density ratio with a transition detection window the same relative size as that in MFM.
	duplex.hypermart.net /books/hards/002-004.html (716 words)

	What is RLL? Run Length Limited, clock data flux reversals. (Site not responding. Last check: 2007-10-09)
		I say that RLL is a family of techniques because there are two parameters that define how RLL works, and therefore, there are several different variations.
		The type of RLL used is expressed as "X,Y RLL" where X is the run length and Y is the run limit.
		Describing how RLL encodes the data would be too involved to include here because it uses specific patterns of reversals to encode patterns of bits, and I've probably gotten more detailed here than I wanted to anyway.
	bugclub.org /beginners/hardware/rll.html (274 words)

	AIM - The global trade assocation for automatic identification
		The length of a bit cell is determined by the average inter-reversal length of the starting zero bits.
		Inter- reversal length of 1 1/2 bit cells starts from the adjacent transition of three possible bit sequences which are {001}, {100} and {010}.
		Run Length Limited (RLL) - MFM is a run length limited code with a maximum distance between flux transitions of two bit cells.
	www.aimglobal.org /technologies/card/mfmencoding.asp (670 words)

	[No title] (Site not responding. Last check: 2007-10-09)
		Run length limited codes are extensions of earlier non return to zero recording (NRZ) codes, where binarily recorded"zeros"are represented by no (magnetic flux) change in the recording medium, while binary"ones"are represented by transitions from one direction of recorded flux to the opposite direction.
		In the meantime, the length r of the digital word is determined such that bit length A of the data word 19 added by r is multiple of m, that is, A+r=cm where c is an arbitrary integer.
		The apparatus set forth in claim 19, wherein said length r of the digital word has been determined such that bit length of the partitioned data segment added by the length r is a multiple of m.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=01/99288.011227&ELEMENT_SET=DECL (4699 words)

	10.2 Run Length Encoding (Site not responding. Last check: 2007-10-09)
		Run length encoding is one of the simplest data compression techniques, taking advantage of repetitive data.
		Runs are represented with a count and the original data byte.
		Runs are then represented as the special character followed by the count followed by the data.
	www.netnam.vn /unescocourse/computervision/102.htm (564 words)

	United States Patent Application: 0040164885
		[0005] In a Run Length Limited (RLL) code represented by (d, k, m, n), the performance of a code is evaluated mainly based on a recording density and a capability to suppress a DC component of the code.
		In the RLL code, however, "d", which is the minimum number of a series of `0s` that can exist between `1` and `1` in a codeword, and "k", which is the maximum number of a series of `0s` that can exist between `1` and `1` in a codeword, should be satisfied.
		According to the method of generating and allocating codewords of source words to be recorded on a recording medium, the codewords satisfying predetermined run length conditions are generated and the generated codewords are grouped according to each run length condition in operation 300.
	appft1.uspto.gov /netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=/netahtml/PTO/srchnum.html&r=1&f=G&l=50&s1="20040164885".PGNR.&OS=DN/20040164885&RS=DN/20040164885 (3794 words)

	Encyclopedia: Run Length Limited
		Group Code Recording (GCR) is a floppy disk data encoding format used by the Apple II and Commodore Business Machines in the 5Â¼ disk drives for their 8-bit computers (the best-known drives being the Disk II for the Apple II family and the Commodore 1541, used with the...
		Run Length Limited, commonly RLL, is the most popular scheme for encoding data on
		RLL encoding was invented by IBM, who used it in
	www.nationmaster.com /encyclopedia/Run-Length-Limited (910 words)

	Run Length Limited (Site not responding. Last check: 2007-10-09)
		RLL packs up to 50% more data on a diskthan its predecessor in the PC market, MFM.
		The density of flux transitions is limited by the spatial resolutionof the disk and frequency response of the head and electronics.
		RLL implementations vary according to the minimum and maximum allowed numbers of transition cells between transitions.For example, the most common variant today, RLL 1,7, can have a transition in every other cell and must have atleast one transition every seven cells.
	www.therfcc.org /run-length-limited-176356.html (210 words)

	Apparatus and method for forming d.c. free codes - Patent 4547890
		A coding scheme in which the length of the symbol is limited is commonly referred to as a run-length limited code.
		Coded sequences may be denoted by parameters such as the shortest run length of zeroes between two consecutive transitions or ones, the longest run length of zeroes between any two transitions or ones and the accumulated charge at any digit position in the sequence.
		While the invention may be used with variable length words, for simplicity, the invention is explained with reference to fixed length words used in varying combinations.
	www.freepatentsonline.com /4547890.html (6223 words)

	ScienceDaily: Run length limited
		Look for Run length limited in Wiktionary, our sister dictionary project.
		Look for Run length limited in the Commons, our repository for free images, music, sound, and video.
		Check for Run length limited in the deletion log, or visit its deletion vote page if it exists.
	www.sciencedaily.com /encyclopedia/run_length_limited (905 words)

	Run-Length Encoding (RLE)
		In such a scheme, the seven least significant bits of the first byte hold the run count minus one, and the most significant bit of the first byte is the indicator of the type of run that follows the run count byte (shown in Figure 9-4, b).
		A run of image data stored as 3-byte pixel values encodes to a 4-byte packet, with one run-count byte followed by three run-value bytes (shown in Figure 9-4, e).
		Remember that the run count in pixel-level RLE schemes is the number of pixels and not the number of bytes in the run.
	www.fileformat.info /mirror/egff/ch09_03.htm (2837 words)

	High Density Bipolar Order 3 Encoding (Site not responding. Last check: 2007-10-09)
		The purpose of this is to prevent long runs of 0's in the data stream which may otherwise prevent a DPLL from tracking the centre of each bit.
		Such a code is sometimes called a "run length limited" code, since it limits the runs of 0's which would otherwise be produced by AMI.
		One refinement is necessary, to prevent a dc voltage being introduced by excessive runs of zeros.
	www.erg.abdn.ac.uk /users/gorry/course/phy-pages/hdb3.html (451 words)

	Run-length encoding - Computing Reference - eLook.org (Site not responding. Last check: 2007-10-09)
		A kind of compression algorithm which replaces sequences ("runs") of consecutive repeated characters (or other units of data) with a single character and the length of the run.
		This can either be applied to all input characters, including runs of length one, or a special character can be used to introduce a run-length encoded group.
		The longer and more frequent the runs are, the greater the compression that will be achieved.
	www.elook.org /computing/run-length-encoding.htm (91 words)

	Run-Length-Limited Encoding Simulation
		RLL is designed to limit the number of consecutive zeroes, and is frequently used to store data on magnetic disks.
		The RLL encoding of the data is then sent to the magnetic disk using NRZI transmission encoding.
		Applets on this website were written by Teresa Carrigan in 2004, for use in computer science courses at Blackburn College, with the exception of the Fireworks applet.
	www.frontiernet.net /~prof_tcarr/RLL-Encoding/RLL-Encoding.html (697 words)

	Servo system including velocity and phase servo circuits for digital audio record disc reproducing apparatus - Patent ...
		This invention relates generally to an apparatus for reproducing an audio or other information signal recorded on a record disc as a pulse code modulation (PCM) in a run length limited code, and more particularly is directed to a servo system for controlling the rotation of the record disc in such reproducing or playback apparatus.
		It is known to provide a digital audio record disc similar to a so-called video record disc, and in which a PCM audio signal is recorded as a series of pits or recesses arranged in a spiral track on the record disc.
		Further, when the run length limited code modulating system is used, each frame of the recorded signal includes a frame synchronizing signal in the form of a bit pattern corresponding to two successive maximum transition intervals T.sub.max or two successive minimum transition intervals T.sub.min.
	www.freepatentsonline.com /4543650.html (7529 words)

	[No title] (Site not responding. Last check: 2007-10-09)
		A run length constraint is imposed on the selected code such that the encoded bit stream has a maximum possible run of seven consecutive same binary symbols in adjacent ones of the plurality of bit positions.
		Encoder 150 also limits the maximum run length of zeros in each of two interleaved sub-sequences within code word stream 153, which are formed by the odd indexed binary digits and the even indexed binary digits, respectively, in code word stream 153.
		In a RLL code of rate m/n, m-bit long data words are mapped into n-bit long code words that satisfy the selected RLL constraints, where m and n are positive integer variables.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=99/67784.991229&ELEMENT_SET=DECL (6264 words)

	HwB: ST506/412 Connector (Offline) (Site not responding. Last check: 2007-10-09)
		Also known as MFM or RLL since these are the encoding methods used to store data.
		Later a new encoding method was developed, RLL (Run Length Limited).
		RLL had the advantage that it was possible to store 50% more with it.
	www.eecis.udel.edu /~girish/HWB/connector/storage/st506.html (110 words)

	Method and apparatus for encoding data with variable block lengths (US5574448)
		bit does not violate the code's run length limitations, either within the cell or within a modulation code word, which is a concatenation of the cells.
		An encoding system for encoding b-bit symbols and e-bit symbols using a modified n/m rate run length limited modulation code that limits the run length of consecutive zero's to z and consecutive one's to r, the system including:
		a cell manipulator for producing, from an n-bit cell associated with an e-bit symbol, an (m+i)-bit cell that satisfies the run length limitations of the modulation code, the manipulator inserting into the n-bit cell the i=e-b bits of the associated e-bit symbol that the encoder refrained from encoding; and
	www.delphion.com /details?pn=US05574448__ (347 words)

	Citations: A Generalized Method for Encoding and Decoding Run-Length-Limited Binary Sequences - Beenker, Immink ... (Site not responding. Last check: 2007-10-09)
		Notice that for an increasing value of n, the number of 1 s in the tail as given by Algorithm 2.2 is non increasing.
		....codeword length is large, the encoder decoder mapping should be such that they can be implemented by an algorithmic procedure rather than by table lookup.
		....Finite length sequences cannot in general be cascaded without offending the given constraints at the boundaries.
	citeseer.lcs.mit.edu /context/785366/0 (1255 words)

	Personal Computer System Components (Site not responding. Last check: 2007-10-09)
		Run Length Limited (RLL) disk drives are no longer used in the industry, but the encoding method is. In fact, it’s the most widely used and popular encoding scheme for hard disks because it can store 50 percent more data on a disk than MFM encoding.
		The RLL disk drive had the same outward appearance as the MFM drive, but the controller cards were typically smaller.
		RLL drives were also connected to the RLL controller card with two cables and used 5.25-inch disk platters.
	www.windowsitlibrary.com /Content/175/02/5.html (1517 words)

	Eight-to-Fourteen Modulation - Wikipedia, the free encyclopedia
		EFM belongs to the class of DC-free Run Length Limited (RLL) codes because it ensures that a) the spectrum (power density function) of the encoded sequence vanishes at the low-frequency end and b) both the minimum and maximum number of consective bits of the same kind are within specified bounds.
		In optical recording systems, servo systems accurately follow the track in three dimensions, radial, focus, and rotational speed.
		Decoding of EFMPlus-generated sequences is accomplished by a sliding-block decoder of length two, that is, two consecutive codewords are required to uniquely reconstitute the sequence of input words.
	en.wikipedia.org /wiki/Eight-to-Fourteen_Modulation (501 words)

	Data Storage-run length limited (Site not responding. Last check: 2007-10-09)
		RLL (Run Length Limited) — An encoding scheme used during write operations to facilitate data...
		It is the number of tracks that is the principle......The encoding method used is either MFM Modified Frequency Modulation) or RLL Run Length Limited) - similar to the way in which data is encoded on a hard...
		RLL (Run Length Limited) An encoding scheme used during write operations to facilitate data readback...
	www.datastoragesearch.com /qry/run+length+limited (605 words)

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