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AMBA AXI-4 Network on Chip designed for HLS

NoCpad provides optimized HLS-ready SystemC models of all required Network-on-Chip components, such as network interfaces and routers (including virtual channels), in order to build a scalable AMBA-compliant SoC interconnect fabric. Quality of results in terms of networking performance as well as hardware PPA matches closely that of custom RTL.

Network interfaces translate AMBA AXI-4 transactions to an internal versatible packetized protocol that is routed through a Network-on-Chip (NoC). Both coherent and non-coherent transactions are supported including AXI4, ACE network interfaces. Furthermore, ACE-Lite interfaces enable agents with no caches (such as DMA controllers or hardware accelerators) to access shareable data and participate in a mixed ACE and ACE-Lite interconnect.

A network on chip connecting IP cores using network interfaces and routers

Link-level communication between components is performed using Connection channels, included in Mentor's Catapult HLS HLSLibs, and MatchLib a SystemC/C++ library of commonly-used hardware functions and components.

Why does it make sense to build a NoC using HLS?

  • NoC can change many times during design flow
    • Changes can be structural and/or architectural
    • Re-verification should be fast
  • SystemC/C++ models abstract enough to be highly configurable
    • Complex customizations can be easily architected
    • C++ simulation is faster
  • HLS constraints can produce the needed result
    • Or even lead to new unexplored alternatives
    • No need for re-verification

NoCpad targets agile interconnect development. The designer of the network fabric can choose across non-coherent AXI-4 interfaces or coherent ACE interfaces to compose an efficent NoC. Data transfer is handled by NoC routers that support simple wormhole or virtual-channel flow control. In all cases, contention is resolved by arbiter modules chosen from a library of various arbiter architectures.

AMBA-AXI4 interfaces :

  • AXI porotocol compatibility
    • All burst types
    • Multiple configurable transaction IDs
    • Arbitrary data lane widths, even under the same interconnect
    • Narrow and unaligned transactions
  • Internal packet based transport protocol
    • Arbitrary internal NoC widths
  • Matchlib AXI class definitions for easy interoperability

AMBA-ACE, ACE-Lite interfaces :

  • ACE porotocol compatibility
    • Various cache line sizes
    • Interconnect's Data channels, are currenty sized depending the chosen cache line width
    • HOME-Node for transaction PoS (Point-of-Serialization) and protocol management
    • Multiple HOME nodes support for load balancing
    • ACE-Lite support for uncached agents
    • Support for the optional snoop data response
    • Mixed coherent and non-coherent traffic
  • Internal packet based transport protocol
  • Extends Matchlib definitions for ACE support, based on the AXI paradigm

NoC Routers :

  • Configurable number of Input/Output ports
  • Various arbitration schemes
  • Able to form arbitrary network topologies
  • Two forms of link-level flow control
    • Wormhole routers with Ready-Valid flow controll using Connections
    • Virtual Channel based usin Connections and credit-based flow control

Library of arbiter components:

  • Fixed Priority
  • Round Robin
  • Matrix arbiter
  • Weighted Round Robin
  • Deficit Round Robin
  • Merged arbiter multiplexers

Getting Started

Tool versions

The codebase is based on Connections and MatchLib, and follows the similar tool/dependency versions:

  • gcc - 4.9.3 (with C++11)
  • systemc - 2.3.1
  • boost - 1.68.0
  • catapult - 10.5a
  • connections - included with catapult
  • QuestaSim - 2019.3_1

Environment requirements

Makefiles and synthesis scripts expect the following environment variables: (A sample bash script can be found in examples/


In addition, the boost and systemc library locations are expected to be in LD_LIBRARY_PATH.

C++ compile and simulate

cd examples/<example>

Mentor Catapult synthesis

cd examples/<example>
catapult -file go_hls_ic.tcl


Dimitris Konstantinou, Giorgos Dimitrakopoulos, Dionisis Filippas

Pending additions

  • AMBA AHB5 network interfaces


NoCpad is licensed under the MIT License.