RLL code

RLL code

[¦är¦el′el ‚kōd]
(communication)
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Hybrid Magneto-Optic-Silicon Memory with an RLL code for Data Compression
RLL code is normally defined by code rules that can support a higher density into a larger sequence of channel bits during encoding.
In the hybrid memory on the encoding side of the digital channel a 16 bit digital data input word stream is replaced by a variable length (2,7) RLL code. Since the (2,7) code words are smaller than 16 bits they require less space so they can be processed at a faster speed.
Assuming that input words 16 bit long are used, then, since subtraction of successive words is required for the channel RLL code, two input words of a total length of 32 bits are required, Taking the example of Figure 1, for (2,7) code, there can be 5 'O's before the 1' and 7 'O's after the '1'
An example of such an inexpensive innovation was the substitution of Run Length Limited (RLL) recording codes for Modified Frequency Modulation (MFM) codes between 1982 and 1988.(21) Development of RLL codes, which enabled a 30 percent improvement in recording density, was a software development project that consumed several hundred thousand to a few million dollars per firm.
Table 6 Numbers of Established and Entrant Firms Introducing Models Equipped with Thin-Film Heads and RLL Recording Codes, 1976-1988 Year Thin Film Heads RLL Codes No.
b) Daisy chaining RLL codes and elimination of need to record unchanged aspects, results in high speed and major reductions in error correction needed.