It is a very useful technique to learn for embedded system, since anecdotally 10% of any hardware engineer’s time is spent (wasted) struggling with serial port communication, for each project. There are plenty of reference material: Wikipedia page and the original paper, even with C source code to get you familiar with the method. Unicode.HDLC introduced a common byte stuffing method (with 0x7D, 0x7E), until the advent of clever COBS. This framing method is only applicable in 8-bit character codes which are a major disadvantage of this method as not all character codes use 8-bit characters e.g. The flag bytes used in the figure 2 used is named as “ESC” flag byte. Two consecutive flag bytes indicate the end of one frame and start of the next one. Each frames starts with and ends with a flag byte.

In this method, start and end of frame are recognized with the help of flag bytes.

For example, some LANs encodes bit of data by using 2 physical bits.

This method of framing finds its application in networks in which the change of data into code on the physical medium contains some repeated or duplicate data.

The figure1 below gives an example of bit stuffing.

Bit Stuffing is completely transparent to network layer as byte stuffing.

When the receiver sees five consecutive incoming i bits, followed by a o bit, it automatically destuffs (i.e., deletes) the 0 bit.

This bit stuffing is similar to byte stuffing, in which an escape byte is stuffed into the outgoing character stream before a flag byte in the data.

In the data a 0 bit is automatically stuffed into the outgoing bit stream whenever the sender's data link layer finds five consecutive 1s.

In his case, each frame starts and ends with a special bit pattern, 01111110.

In this method, frames contain an arbitrary number of bits and allow character codes with an arbitrary number of bits per character.

When five consecutive l's are encountered in the data, it automatically stuffs a '0' bit into outgoing bit stream. Each frame begins and ends with a special bit pattern, 01111110 called a flag byte.The frames are separated by separating flag. Allows frame to contain arbitrary number of bits and arbitrary character size.

Advantages of byte styuffing