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.

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

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

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

• CATAPULT_HOME
• SYSTEMC_HOME
• BOOST_HOME
• MATCHLIB_HOME

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

cd examples/<example>
make
./sim_sc 

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

Dimitris Konstantinou, Giorgos Dimitrakopoulos, Dionisis Filippas

• AMBA AHB5 network interfaces

NoCpad is licensed under the MIT License.