NEXT (ESL Flow Model: Avoiding ISS/RTL overheads using native calls.)
ESL: Electronic System Level Modelling
Recall the following levels of modelling from the start of this course:
- Functional Modelling: The `output' from a simulation run is accurate.
- Memory Accurate Modelling: The contents and layout of memory is accurate.
- Untimed TLM: No time stamps recorded on transactions.
- Loosely-timed TLM: The number of transactions is accurate, but order may be wrong.
- Approximately-timed TLM: The number and order of transactions is accurate.
- Cycle-Accurate Level Modelling: The number of clock cycles consumed is accurate.
- Event-Level Modelling: The ordering of net changes within a clock cycle is accurate.
An ESL methodology aims:
Aim 1: To model with good performance the a SoC using full software/firmware.
Aim 2: To allow seamless and successive replacement of high-level parts of the model
with low-level models/implementations when available and when interested in their detail.
So, an ESL methodology must provide:
Chosen baseline methodolody: SystemC Transactional Modelling using high-level models in C++.
- Tangible, lightweight rapidly-generated prototype of full SoC architecture.
- Rapid Architectural Evaluation: determine bus bandwidth and memory use for
a candidate architecture. Easy to adjust major design parameters.
- Algorithmic Accuracy: Get real output from an early system,
hosting the real application/firmware, possibly in real-time.
- Timing information:
Get timing numbers for performance (accurate or loose timing).
- Power information:
Get power consumption estimates to evaluate chip temperature and system battery life.
- Firmware development: Integrate high-level behavioural models of major components
with their device drivers to run test software and applications.
- Synthesise high-level models to form parts of the
fabricated system (see elsewhere notes on HLS)(but today manual re-coding is mainly used).
- Embed assertions in the high-level models and use these same
assertions through to tape out (see later section ABD).