Register transfer level power optimization with emphasis on glitch analysis and reduction

We present design-for-low-power techniques for register-transfer level (RTL) controller/data path circuits. We analyze the generation and propagation of glitches in both the control and data path parts of the circuit. In data-flow intensive designs, glitching power is primarily due to the chaining of arithmetic functional units. In control-flow intensive designs, on the other hand, multiplexer networks and registers dominate the total circuit power consumption, and the control logic can generate a significant amount of glitches at its outputs, which in turn propagate through the data path to account for a large portion of the glitching power in the entire circuit. Our analysis also highlights the relationship between the propagation of glitches from control signals and the bit-level correlation between data signals. Based on the analysis, we develop techniques that attempt to reduce glitching power consumption by minimizing propagation of glitches in the RTL circuit. Our techniques include restructuring multiplexer networks (to enhance data correlations and eliminate glitchy control signals), clocking control signals, and inserting selective rising/falling delays, in order to kill the propagation of glitches from control as well as data signals. In addition, we present a procedure to automatically perform the well-known power-reduction technique of clock gating through an efficient structural analysis of the RTL circuit, while avoiding the introduction of glitches on the clock signals. Application of the proposed power optimization techniques to several RTL circuits shows significant power savings, with negligible area and delay overheads.