Run length Limited

run length Limited (RLL) is a recording mode with disk memories, with that a higher memory density becomes possible than with the Modified frequency modulation - procedure (MFM). Since RLL is based on similar principles as MFM, RLL is a direct advancement of MFM.

RLL is historicala successor of the MFM recording mode and the predecessor of current procedures such as Partial Response/maximum Likelihood (PRML) and their advancement EPRML. These new procedures have however completely different technical bases than RLL.

Types: RLL 1,7, RLL 2,7, RLL 2.9.

The recording method RLL1.7 means thatbetween two changes in the direction of magnetization, which represent a “1”, at least one and at the most 7 zeros lie. Any consequence of zero and unity is then converted into a consequence with this characteristic. Thus becomes the recording method internal clock generation-end: with approximate default of the rotational speed can itselfthe read write unit again and again synchronize.


 

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