Virtual channel bus and system architecture

Abstract

A processor system includes an on-chip, split-transaction bus with independent address/control and data buses. Arbitration and bus acquisition protocols are performed on the address/control bus. An arbiter arbitrates I/O requests and regulates concurrent ownership of the split-transaction bus by assigning a virtual channel to each bus request. Data bus access is granted to a virtual channel on a priority basis, s so as to utilize to a maximum extent the available bandwidth of the data bus. In one embodiment, the data bus is preempted by another virtual channel when current virtual channel using the data bus becomes idle due to, for example, latencies in the data stream. Rearbitration, however, is avoided when the interrupted data transfer resumes, owing to state information regarding the data transfer stored in the master and slave modules of each virtual channel.