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

Abstract

A symbol-wide elasticity buffer for a receive/transmit station within an asynchronous data transmission network provides both for reframing after each packet and for the handling of a continuous line state symbol for a period longer than the allowed packet size. According to one aspect of the invention, the elasticity buffer is divided into a START section and a CONTINUATION section. The buffer's write pointer will not enter the CONTINUATION section until the read pointer is directed to the first of the multiple, sequential registers comprising the START section. The read pointer must sequentially read the START section registers before entering the CONTINUATION section. Once the write pointer or read pointer leaves the START section, it can only reenter the START section upon receipt of a start delimiter signal. When the write pointer or the read pointer reaches the last register in the CONTINUATION section, it is automatically routed back to the first CONTINUATION section register. According to a second aspect of the invention, a repeat flag is associated with the last register in the CONTINUATION section. The repeat flag is set upon receipt of any repeatable control signal. With the Repeat Flag set, the read pointer will reach the final CONTINUATION section register and continue to read the same symbol without causing an overflow or underflow. When a new symbol is received, a CONTINUE signal is generated and the write pointer begins writing to the CONTINUATION section. After a predetermined delay, the read pointer begins reading the first register in the CONTINUATION section and the R-Flag is cleared.