Asynchronous on-Chip Communication: Explorations on the Intel PXA27x Processor Peripheral Bus

For today's SoC designer, on-die variation, clock distribution, timing closure, and power concerns confront the desire to get products to market quicker. Each new process generation makes the challenge greater as process skews, complexity, and frequency become more onerous. This is particularly true for signals that have to travel across larger portions of a chip such as clocks and buses. In this paper, we examine the use of GALS (Globally Asynchronous, Locally Synchronous) [Chapiro, 1985] techniques to address on-chip communication between different synchronous modules on a bus. We explore issues related to validation, module interfaces and tool flows, while looking at advantages in power savings, timing closure and Time-to-Market/Time-to-Money (TTM). Our exploration vehicle is the IntelregPXA27x Peripheral Bus (PB) - a common interface for connecting peripherals on PXA27x and related processor families in Intel's cellular and handheld application and communication domain.