Design of a digital crossbar/crosspoint switch for TMS320C40 Digital Signal Processors

The design of an eight-port digital crossbar/crosspoint switch is presented. An N-port crossbar switch,/i> is an interconnection device in a multiprocessor system which allows connection between pairs of data ports of different processors. There are a total of N/2 connections possible at a time, where N is the number of ports attached. A crosspoint switch allows any one of the ports to broadcast its data to as many of the other ports as desired, giving a possibility of N-1 connections. This design provides both these interconnections between eight communication ports of Texas Instruments' TMS320C40 (C40) Digital Signal Processors in a parallel processing system. The eight-port switch design proves the concepts necessary to expand to a larger switch, specifically a thirty-two port switch. The design is based on LSI Logic's Crossbar Switch VLSI chip and utilizes large programmable logic devices to handle data transfer handshaking, data bus direction changing, and configuration handshaking between the switch and the control unit. The control unit consists of a remote C40 connected to the switch through a memory expansion protocol, and the appropriate control software. The switch was tested for data path integrity and throughput rate. A data rate of 6.6 to 7.2 Mbytes/sec through the switch was achieved using 40 Mhz C40s, demonstrating the switch's usefulness in a parallel processing system. Expansion to larger switches, specifically a thirty-two port switch, is also discussed.