Puneet Arora ESCUG, 09 Abstraction Levels in SoC Modelling

Agenda Introduction Abstraction levels Terminologies Implementation Implementation Example Adaptors Conclusion and References

Introduction SoC Modelling: Software model / Executable representation of SoC Various use cases –Functional verification –Early s/w development –HW/SW partitioning, resource sharing –Architecture Exploration –Verify memory and bus designs –Cycle accurate h/w models

Abstraction Levels Required to cater to different use-cases Control amount and frequency of communication Control simulation speed and accuracy SystemC signal: RTL TLM2.0 (Payload / Phases): Higher abstractions

Terminologies.. Popular Terminology Programmer's View: functional correct, fast models for embedded software development Architect's View: explore design features like bus-width, memory organization, die-area etc Verification View: cycle-accurate modelling, simulate actual timing and memory requirements, closest to RTL

Terminologies.. OCP-IP modelling kit Introduces four levels –TL1: cycle accurate modelling, supports all dataflow signals of OCP through extensions and phases –TL2/TL3: approximate timed modelling, fewer extensions and phases –TL4: loosely timed modelling, phases are not used, blocking transport mechanism is used –Compatible with OSCI BP wherever possible

Terminologies.. OSCI TLM2.0 Provides generic framework for memory mapped busses Defines a Base protocol Provides infrastructure for extending base protocol to model at different abstraction levels Recommends two coding styles Abstraction levels not well defined

Terminologies.. STARC TLM Guideline Uses timing and data granularity axis to define abstraction levels Combines points on these axis to define Abstraction levels Timing : UnTimed, ApproximatelyTimed, CycleAccurate Data : TRansaction, BusPhase, BusCycle, BusSignal

Source: STARC TL Guideline, 2 nd Edition Terminologies..

Timing Accuracy Data Granularity Mapping of the OSCI Abstraction Levels

Terminologies.. Timing Accuracy Data Granularity Mapping of the OCP Abstraction Levels

Source: STARC TL Guideline, 2 nd Edition Mapping UseCases

Implementation By extending OSCI TLM2.0 –blocking and non_blocking transport APIs –blocking can use wait, temporal decoupling –non_blocking uses phases and PEQs –Extend protocol for lower abstraction levels or bus specific features typedef generic_payload Define new payload Define new phases

Implementation Example OCP-IP Modelling Kit Support for advanced communication protocols at various abstraction levels –Built on top of TLM2.0 –Payload extensions –Phase extensions –Master Sockets with memory management for payload and extensions –Slave sockets with PEQ for timing annotations

Implementation Example.. OCP-IP TL1 Cycle accurate using extensions & phases Support for individual beats of burst transfers Different from OSCI BP –Enforces END_X for every BEGIN_X –Allows phase overlap –Disallows use of TLM_COMPLETED(no shortcuts)‏ –Modules synchronized at boundary of same clock and supports non-default timing

Implementation Example..

OCP TL2 Used for Approximate Timed coding styles Acts as bridge between TL1 and TL3 Phases like TL1 but exact clocking is optional Used for intra-burst timing Implementation Example..

OCP TL3 Data phases are not used Some extensions are not used as intermediate timing is not captured Maximum interoperability with OSCI BP Different bursts are indistinguishable as data transfer completes in one go Synchronized at interface method calls Implementation Example..

TL3 example : phases same as OSCI BP Implementation Example..

TL3 example : request_accept_delay and response latency is zero Implementation Example..

OCP TL4 loosely timed coding style of OSCI BP Phases are not used Transfer completes when b_transport returns Detail timing behavior not modelled Implementation Example..

Adapters TL3 Slave RTL Master TL1 Module InterConnect Models at different abstraction levels are to be connected -Skip intermediate phases by combining them -May need to arrange data within themselves

TL1 Master to TL3 Slave TL1 MTL3 SAdapter Beg_Resp Beg_Req Beg_Data Beg_Req End_Resp Adapters

TL4 M TL4 Master to TL3 Slave TL3 SAdapter b_transport nb_tr ( beg_req)‏ nb_tr ( beg_resp)‏ wait()‏ Return b_transport Adapters

Conclusion OSCI TLM2.0 can be extended to implement different abstraction levels. OCP-IP TLM Kit extends TLM2.0 for OCP-IP bus protocol. Models at different abstraction levels can be easily connected using adapters

References OSCI TLM2.0 User Manual OCP-IP TLM Modelling Kit Manual STARC TLM Guide, 2 nd Edition

Questions SoC Modelling Services (SystemC, TLM2.0)‏