A 622-Mb/s 8*8 ATM switch chip set with shared multibuffer architecture

Abstract

An asynchronous transfer mode (ATM) switch chip set, which employs a shared multibuffer architecture, and its control method are described. This switch architecture features multiple-buffer memories located between two crosspoint switches. By controlling the input-side crosspoint switch so as to equalize the number of stored ATM cells in each buffer memory, these buffer memories can be treated as a single large shared buffer memory. Thus, buffers are used efficiently and the cell loss ratio is reduced to a minimum. Furthermore, no multiplexing or demultiplexing is required to store and restore the ATM cells by virtue of parallel access to the buffer memories via the crosspoint switches. Access time for the buffer memory is thus greatly reduced. This feature enables high-speed switch operation. A three-VLSI chip set using 0.8- mu m BiCMOS process technology has been developed. Four aligner LSIs, nine bit-sliced buffer-switch LSIs, and one control LSI are combined to create a 622-Mb/s 8*8 ATM switching system that operates at 78 MHz. In the switch fabric, 155-Mb/s ATM cells can also be switched on the 622-Mb/s port using time-division multiplexing. >