Difference between revisions of "Modified Frequency Modulation"
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| − | '''Modified Frequency Modulation''' is an encoding technique, used in [[magnetic storage]] such as [[disk]]s and [[Disk#Low-cost disks|floppy drive]]s. | + | '''Modified Frequency Modulation''' (also '''MFM''') is an encoding technique, used in [[magnetic storage]] such as [[disk]]s and [[Disk#Low-cost disks|floppy drive]]s. |
| − | It is, as the name says, a modification of the earlier [[Frequency Modulation]] scheme used in the same applications; instead of a clock transition and possibly also an additional data transition in each bit time, in MFM there is at most one transition per bit time. This allows twice as many bits to be encoded | + | It is, as the name says, a modification of the earlier [[Frequency Modulation]] scheme used in the same applications; instead of a clock transition and possibly also an additional data transition in each bit time, in MFM there is at most one transition per bit time. This allows twice as many bits to be encoded for a given maximum transition rate. |
To be exect, in MFM there is a reversal (signal level, or magnetic flux) at the bit time for a '1', and no reversal for a '0'. A reversal ''between'' data bit times occurs with consecutive zeros. | To be exect, in MFM there is a reversal (signal level, or magnetic flux) at the bit time for a '1', and no reversal for a '0'. A reversal ''between'' data bit times occurs with consecutive zeros. | ||
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Revision as of 17:32, 25 October 2017
Modified Frequency Modulation (also MFM) is an encoding technique, used in magnetic storage such as disks and floppy drives.
It is, as the name says, a modification of the earlier Frequency Modulation scheme used in the same applications; instead of a clock transition and possibly also an additional data transition in each bit time, in MFM there is at most one transition per bit time. This allows twice as many bits to be encoded for a given maximum transition rate.
To be exect, in MFM there is a reversal (signal level, or magnetic flux) at the bit time for a '1', and no reversal for a '0'. A reversal between data bit times occurs with consecutive zeros.
