bit stuffing การใช้

• The active error flag consists of six consecutive dominant bits and violates the rule of bit stuffing.
• Bit stuffing may be used to synchronize several channels before multiplexing or to rate-match two single channels to each other.
• Similar techniques are used to combine four & times; 8 Mbit / s together, plus bit stuffing, giving 34 Mbit / s.
• In the fields where bit stuffing is used, six consecutive bits of the same type ( 111111 or 000000 ) are considered an error.
• For example, HDLC uses bit stuffing or " octet stuffing ", while other systems use ASCII armor or Consistent Overhead Byte Stuffing ( COBS ).
• 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.
• To ensure a minimum density of signal transitions remains in the bitstream, USB uses bit stuffing; an extra 0 bit is inserted into the data stream after any appearance of six consecutive 1 bits.
• Bit stuffing is used for various purposes, such as for bringing bit streams that do not necessarily have the same or rationally related bit rates up to a common rate, or to fill frames.
• Bit stuffing ensures that this pattern can never occur in normal data, so it can be used as a marker for the beginning and end of frame without any possibility of being confused with normal data.
• While bit stuffing is efficient, it results in a variable data rate because it takes slightly longer to send a long string of 1 bits than it does to send a long string of 0 bits.
• Bit stuffing does not ensure that the payload is intact ( " i . e . " not corrupted by transmission errors ); it is merely a way of attempting to ensure that the transmission starts and ends at the correct places.
• "' Flag "' The value of the flag is always 0x7E . In order to ensure that the bit pattern of the frame delimiter flag does not appear in the data field of the frame ( and therefore cause frame misalignment ), a technique known as Bit stuffing is used by both the transmitter and the receiver.
• 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.