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Interaction of SystemC AMS Extensions with TLM 2.0

Interaction of SystemC AMS Extensions with TLM 2.0. Markus Damm , Christoph Grimm Vienna University of Technology Martin Barnasconi NXP Semiconductors. Embedded AMS systems. AMS-TLM interface. Receiver. Serial Interface. Modulator/ demod. DSP. Host processor. Antenna front-end.

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Interaction of SystemC AMS Extensions with TLM 2.0

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  1. Interaction of SystemC AMS Extensions with TLM 2.0 Markus Damm, Christoph GrimmVienna University of Technology Martin Barnasconi NXP Semiconductors

  2. Embedded AMS systems AMS-TLM interface Receiver Serial Interface Modulator/ demod. DSP Host processor Antenna front-end ADC Calibration & Control Micro- controller SystemC AMS SystemC TLM Memory Imaging DSP Transmitter DAC to all blocks Audio DSP High Speed Serial Interface Power Manage- ment RFdetector Temp.sensor Oscillator Clock Generator • Tight interaction between AMS and digital HW/SW sub-systems • Dedicated interfaces between analog and digital domain • How should a TLMAMS interface be defined?

  3. SystemC AMS TDF …implies a samlingperiodof 20 s here! Sine-source “TDF-Cluster“ A 20 s 50 20 s 100 C D 20 s 20 s 100 1 B 1 2 ms 1 01001100 Environment 2 ms Modulation e.g. samplingperiodof 2 mshere… Bit-source datarates Schedule: B A A C D…D 100x • Timed DataFlow – Synchronous Dataflow with timing annotation • Enables static scheduling – fast simulation of sampled analog signals at discrete time points • Sampling period associated to token production/consumption

  4. SystemC AMS – SystemC synchronization • SystemC AMS has its own execution semantics and simulation time  synchronization needs! • SystemC AMS provides converter ports which allows TDF modules to connect to usual SystemC Discrete Event signals. • Accessing these ports triggers synchronization to SystemC kernel • Note: SystemC AMS is temporally decoupled, similar to the TLM 2.0 loosely timed coding style! Ifthedata rate is > 1, thedatatokeneven “warp ahead“ tTDF ! Note that tTDF tDEalways holds!

  5. Requirements for AMS-TLM interface • Avoid “signal-level” interface (DETDF converter ports) between AMS and TLM • avoid unnecessary kernel context switching • maintain concept of “loosely coupled independent processes”:avoid strict timing synchronization between processes • Create direct interface between AMS Timed Data Flow and TLM 2.0 Loosely-timed coding style • maintain temporal decoupling for both engines • efficient packing an unpacking of “analog samples” (data) in/from transactions • Introduction of specialized converter modules / channels • can be instantiated and configured by the user • part of design refinement methodology

  6. Basic idea of a generic TLMTDF converter TLMTDF converter TDF submodule TDF-CLUSTER TLMInterconnect dummy DE signal TDF submodule DETDF converter port • WRITE transaction data is streamed to TDF cluster directly • Incoming TDF “samples” are passed to READ transactions • The converter has to be part of the TDF-cluster • Transactions mostly won’t come in regularly  We use buffers which are accessed via transactions • The TDF cluster might run ahead too far in time  We need synchronization means! input-buffer output-buffer …and: what means “too far” exactly?

  7. Implementation • Our current conversion approach assumes loosely timed initiators • Blocking interface, no backward path used • Initiators may use temporal decoupling • Issues: • Transactions may arrive out of order (delays) we need buffers which also keep timing information • If a write-transaction has a delay annotation, the converter doesn’t know if the buffer has enough space by that time we need a projected free buffer space concept • TLM and TDF might warp ahead too much of each other we need to trigger synchronization

  8. TLMTDF converter implementation WRITE-transactions TLM  TDF converter TDF submodule TDF-CLUSTER TLMInterconnect • The output buffer keeps the timestamp of the transaction the respective data was sent with (similar to payload event queue). • If the TDF sub-module fires, it uses only data with a timestamp  the current SystemC AMS time • If an incoming transaction has a delay > 0, a projected free buffer space is computed • the transaction is returned with an error if the (projected) free buffer space is too small for the data • Synchronization:buffer underrun output-buffer

  9. TDFTLM converter implementation READ-transactions TDF  TLM converter TDF submodule TDF-CLUSTER TLMInterconnect • If the TDF submodule fires, the incoming data token are copied into the input buffer (usual FIFO). • We store only the timestamp of the oldest buffer token • Transactions are annotated with an delay according to the timestamp of the youngest token returned • If buffer holds not enough data for the read request, an error is returned • Synchronization: buffer overflow input-buffer

  10. Conclusion / future work • Connecting TLM2 and SystemC AMS models makes sense regarding the design of mixed signals SoCs • Efficient communication between AMS and digital HW/SW part • Sophisticated synchronization • TLM2 temporal decoupling processes can work well together with SystemC AMS statically scheduled TDF processes. • The presented work is a technical feasibility analysis, more groundwork has to be done. • Study Approximately-timed initiators and converter channels • Apply methods to Real-life demonstrator

  11. Your: • questions • comments • ideas • objections Thank you for your attention!

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