Power Consumption of Fault Tolerant Codes: the Active Elements

On-chip global interconnections in very deep submicron technology (VDSM) ICs are becoming more sensitive and prone to errors caused by power supply noise, crosstalk noise, delay variations and transient faults. Error correcting codes can be employed in order to provide signal transmission with the necessary data integrity. We compared Dual Rail encoding versus Hamming with respect to power consumption of the bus wires themselves (passive capacity model) [13]. In this paper we analyze the contribution of the active elements of both coding schemes. We first present a detailed analysis of the power consumption of an encoded bus, taking into account the bus wires (with mutual capacitances, drivers, repeaters and receivers), as well as the encoding/decoding circuitry. Then we compare the two considered coding technique with respect to the power consumption, and we show how different tradeoffs can be achieved. Our analysis is based on a realistic bus structure, implemented in a 0.13 CMOS technology.