Asynchronous design: an enabler for flexible microelectronics

Summary form only given. Flexible microelectronics technology featuring low-temperature polysilicon (LTPS) TFT and surface free technology by laser annealing and ablation (SUFTLAR) is expected to become a platform for developing thin, flexible and low-cost display devices. LTPS TFTs are good for realizing large area displays and integrated circuits at lower cost. A drawback of LTPS TFTs, however, is that they have substantial deviations in characteristics, which are caused by deviations mainly in crystal grain size and thickness of silicon-oxide. Until now, these deviations were considered to be beyond the capability of synchronous circuit design, especially for large-scale circuits such as microprocessors driven by global clocking. Since asynchronous circuits are "self-timed", they absorb the deviations of device characteristics. Plus they run as faster as possible in event-driven fashion dissipating less power, and remain on standby for quick service. Even with the benefits of asynchronous circuits, it is considered difficult to proceed with circuit design using syntax-directed translation using VLSI programming languages such as CSP, Tangram and OCCAM, syntax of which is far from the standard HDL. The authors then decided to develop Verilog+ that comprises a subset of Verilog HDLR and minimal primitives used for describing the communications between processes. Flexible 8-bit asynchronous microprocessor ACT11 is the first successful instance of asynchronous design using Verilog+ without knowledge of element and wire delay except for datapath