Symbol-wide elasticity buffer with a read-only section and a read-write section

An elasticity buffer for use in a data terminal of a data communications system and of the type that includes a write pointer synchronized to a receive clock recovered from an input signal to the data terminal for writing data included in the input signal into the elasticity buffer and a read pointer synchronized to a local clock generated at the data terminal for reading data from the elasticity buffer, the elasticity buffer comprising:

• a plurality of sequential registers which define a START section which includes a plurality of read-only registers followed by a plurality of read-write registers and a CONTINUATION section which follows the START section and includes plurality of read-write registers;
• means for synchronizing a predetermined signal to the local clock;
• means responsive to a power up signal for directing the read pointer to the first read-only register in the START section;
• means responsive to the synchronized predetermined signal for initiating the write pointer at the first read-write register in the START section for sequential movement through the elasticity buffer registers in accordance with cycles of the receive clock signal and for simultaneously initiating sequential movement of the read pointer through the elasticity buffer registers in accordance with cycles of the local clock signal such that when the write pointer and the read pointer reaches the last register in the CONTINUATION it is routed back to the first register in the CONTINUATION section, forming a cyclic buffer queue.

A method of synchronizing the writing of received symbols to storage in an elasticity buffer utilizable in a data terminal in accordance with the cycles of a receive clock signal recovered from an input signal to the data terminal, the input signal including the received symbols, and the reading from elasticity buffer storage of stored received symbols for retransmission by the data terminal in accordance with the cycles of a local clock signal generated at the data terminal, wherein the elasticity buffer comprises an elasticity buffer core comprising a first section that includes a first plurality of sequentially-arranged storage elements for storing symbols and a second section comprising a second plurality of sequentially-arranged storage elements for storing symbols, the method comprising:

• (a) in response to a predetermined write signal provided at a write initiate cycle of the receive clock signal, initiating the sequential writing of symbols to the elasticity buffer core beginning with a first preselected storage element of the first section and continuing sequentially first through storage elements of the first section subsequent to the first preselected storage element and then through the sequentially-arranged storage elements of the second section;
• and
• (b) in response to a predetermined read signal provided at a read initiate cycle of the local signal, the read initiate cycle being subsequent to the write initiate cycle, initiating the reading of symbols from the elasticity buffer core beginning with a second preselected storage element prior to the first preselected storage element in the sequence of storage elements comprising the first section and continuing sequentially first through storage elements of the first sections subsequent to the second preselected storage element and then through the sequentially-arranged storage elements of the second section.