Bit stuffing for synchronous HDLC

A transmission method in a HDLC system using bit stuffing, adding of an extra character in sequences in the original information bits to be transmitted which resembles any flag pattern, and adding a start/stop flag in front of and after the bits to be transmitted, defining a frame to be transmitted;

• which method comprises the steps of:
• creating a first queue of said bits to be transmitted;
• selecting the n first bits from said first queue, creating a first bit sequence of n bits;
• comparing said first bit sequence with prestored transmission bit stuffing data, comprising, for each possible combination of bit values in said first bit sequence, transmission shift data and transmission sequence data;
• adding data derived from the transmission sequence data corresponding to said first bit sequence to a second queue;
• removing a number of bits from said first queue equal to the transmission shift data corresponding to said first bit sequence;
• transmitting data from said second queue;
• repeating all steps until said first queue contains less than n bits and adding the remaining bits in said first queue to said second queue.

A method for bit stuffing in a receiver unit in a HDLC system, cancelling an extra character in sequences in the original information bits received which resembles any flag pattern, which method comprises the steps of:

• selecting the n first bits from a first queue of bits, consisting of said original information bits, creating a first bit sequence of n bits;
• comparing said first bit sequence with prestored reception bit stuffing data, comprising, for each possible combination of bit values in said first bit sequence, reception shift data and reception sequence data;
• adding data derived from the reception sequence data corresponding to said first bit sequence to a second queue;
• and
• removing a number of bits from said first queue equal to the reception shift data corresponding to said first bit sequence;
• repeating all steps until said first queue contains less than n bits and adding the remaining bits in said first queue to said second queue.