Synchronous bus and bus interface device

Abstract

A high performance bus and bus interface device for interconnecting numerous devices without using dedicated high current drivers at each device. The bus is synchronous and divided into a plurality of primary local busses and at least one global bus. Data can be transferred from a first device over a first primary local bus through a first global transceiver, over the global bus to a second global transceiver, and then to a second device through a second primary local bus. The bus is driven to a known state at the end of each burst of data transmitted by a device, before the bus is relinquished to another device. Buffers are provided in each device on the primary local bus which can be accessed by other devices. Buffer management includes: (1) determination by each transmitting device of buffer availability at each receiving device; (2) 'claiming' use by the transmitting device of a buffer in the receiving device for transfers from the transmitting device, including locking out other devices from writing to that buffer; (3) capability of the transmitting device to move received data to the buffer in the receiver; and (4) notification to all devices that the transfer is complete. The bus is used to transfer data between ports of a LAN bridge or switch. A dedicated lookup bus allows address lookup logic to be accessed without arbitrating for the data bus. A distributed CAM is used to perform address lookup functions.