run length limited การใช้
- Most of these codes can be seen as a kind of Run Length Limited code.
- Run length limited ( RLL ) controllers used data compression to increase storage capacity by about 50 %.
- Another use of bit stuffing is for run length limited coding : to limit the number of consecutive bits of the same value in the data to be transmitted.
- NRZ is not inherently a self-clocking signal, so some additional synchronization technique must be used for avoiding bit slips; examples of such techniques are a run length limited constraint and a parallel synchronization signal.
- Run length limited sequences are characterized by two parameters, " d " and " k ", which stipulate the minimum and maximum zero-bit run length that can occur in the sequence.
- Ones-density is often controlled using precoding techniques such as Run Length Limited encoding, where the PCM code is expanded into a slightly longer code with a guaranteed bound on ones-density before modulation into the channel.
- To ensure frequent transitions, some sort of self-clocking signal is used, often a run length limited encoding; 8b / 10b encoding is very common, while Manchester encoding serves the same purpose in old revisions of 802.3 local area networks.
- However, even NRZI can have long series of zeros ( or ones if transitioning on " zero " ), and thus clock recovery can be difficult unless some form of run length limited ( RLL ) coding is used in addition to NRZI . Magnetic disk and tape storage devices generally use fixed-rate RLL codes, while USB uses bit stuffing, which inserts an additional 0 bit after 6 consecutive 1 bits, thus forcing a transition.