MFM Encoding

[nairb]

Hi Dudes

I gotta question for you!!! Using 4-bit Binary will 5 encode using MFM without a preceding digit, why?

any help would be great

[geebee76]

Hi nairb, I think this explanation will answer your question.


Because of the way that encoding takes place with MFM you would need to know what preceded the last digit.
A binary 1 is stored as a non-transition followed by a transition (NT)
but a binary zero is stored as transition followed by a non-transition (TN) if preceded by a 0
and as a non transition followed by another non-transition (NN) if preceded by a 1.

The decimal number 5 would be written in binary as 0101
and therefore as ?? NT NN NT

As you can see, we know that the first "1" (reading from the right) is stored as NT, then the "0" as NN because we can see a "1" to the left of it, then another NT for the next "1" but we don't know what to put for the last "0"

Hope this helps http://www.PCGuide.com/ubb/smile.gif

[This message has been edited by geebee76 (edited 07-17-2001).]