Two-Dimensional Regular Expressions for Compositional Bus Protocols

Bus and interconnect protocols contain a few core operations (such as read and write transfers) whose behaviors interleave to form complex executions. Specifications of the core operations should be flexible enough that simple composition operators suffice for capturing most interleavings, even in the presence of common hardware issues such as glitches. Oliveira and Hu proposed a form of pipelined regular expressions to specify atomic protocol compositions, but they abstracted away clocking and glitches. This paper uses the AMBA-2 specification to argue that a loosely-synchronized form of regular expressions handles such timing subtleties while retaining the simplicity of Oliveira and Hu´s pipelined compositions.