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FM method

The FM( frequency modulation) method is an older recording method for floppy disks and hard disks, which was later superseded by the MFM method and Run Length Limited( RLL).

In the FM method, the storage area for the data is divided into bit cells, where a bit cell represents the area on a disk surface where a single bit is stored. Each bit cell is divided for the clock bit and the data bit.

FM method for data storage on floppy disks

FM method for data storage on floppy disks

The clock bit is used for synchronization and is located before the data bit. It determines where the storage element for the data bit begins. This is necessary to be able to resolve long sequences of "zeros" or "ones". Since the clock changesare stored and therefore need memory space, only a reduced part is available for data storage. This disadvantage is reduced by the MFM method, Modified Frequency Modulation (MFM) and the improved Modified Frequency Modulation( MMFM).

Informations:
Englisch: FM method
Updated at: 22.12.2011
#Words: 158
Links: fault management (FM), frequency modulation (FM), method, modified frequency modulation (Disk) (MFM), run length limited (RLL)
Translations: DE
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