Cycle and phase accurate DSP modeling and integration for HW/SW co-verification

Abstract

We present our practical experience in the modeling and integration of cycle/phase-accurate instruction set architecture (ISA) models of digital signal processors (DSPs) with other hardware and software components. A common approach to the modeling of processors for HW/SW co-verification relies on instruction-accurate ISA models combined (i.e. wrapped) with the bus interface model (BIM) that generate the clock/phase-accurate timing at the component's interface pins. However, for DSPs and new microprocessors with complex architectural features this approach is from our perspective not acceptable. The additional extensive modeling of the pipeline and other architectural details in the BIM would force us to develop two detailed processor models with a complex BIM API between them. We therefore propose an alternative approach in which the processor ISAs themselves are modeled in a full cycle/phase-accurate fashion. The bus interface model is then reduced to just modeling the connection to the pins. Our models have been integrated into a number of cycle-based and event-driven system simulation environments. We present one such experience in incorporating these models into a VHDL environment. The accuracy has been verified cycle-by-cycle against the gate/RTL level models. Multiprocessor debugging and observability into the precise cycle-accurate processor state is provided. The use of co-verification models in place of the RTL resulted in system speedups up to 10 times, with the cycle-accurate ISA models themselves reaching performances of up to 123 K cycles/s.