System-level modeling of energy in TLM for early validation of power and thermal management

Modern systems-on-a-chip are equipped with power architectures, allowing to control the consumption of individual components or subsystems. These mechanisms are controlled by a power-management policy often implemented in the embedded software, with hardware support. Today´s circuits have an important static power consumption, whose low-power design require techniques like DVFS or power-gating. A correct and efficient management of these mechanisms is therefore becoming non-trivial. Validating the effect of the power management policy needs to be done very early in the design cycle, as part of the architecture exploration activity. High-level models of the hardware must be annotated with consumption information. Temperature must also be taken into account since leakage current increases exponentially with it. Existing annotation techniques applied to loosely-timed or temporally-decoupled models would create bad simulation artifacts on the temperature profile (e.g. unrealistic peaks). This paper addresses the instrumentation of a timed transaction-level model of the hardware with information on the power consumption of the individual components. It can cope not only with power-state models, but also with Joule-per-bit traffic models, and avoids simulation artifacts when used in a functional/power/temperature co-simulation.