The Inter-NoC Interface (INI) provides a means of connecting two NoC instances (either axi_noc or axis_noc). An INI link represents a logical connection within the physical NoC that is resolved at the time the NoC compiler is called.
The INI does not directly represent NoC resources, instead the INI connectivity is implemented in the switch network by the NoC compiler. It represents a connection from an NMU in one AXI NoC instance to one or more NSUs or DDRMCs in another instance. An INI port can be an input or an output from an instance of the axi_noc or axis_noc. An INI output port on one NoC instance can connect only to an INI input port on another. An INI input or output port appears in the connectivity matrix like any AXI input or output port, allowing connectivity from an AXI input (NMU) to an INI output, or from an INI input to an AXI output or DDRMC port.
Quality of Service traffic-class for a path that includes an INI connection must be specified at the NMU. Quality of Service bandwidth and other per-path settings must be set in the axi_noc that owns the path. The axi_noc QoS page displays the ownership information. INI paths must terminate within the Vivado IP integrator and must not traverse RTL hierarchy.
INI can be connected in a 1:N topology, which is one NMU with fanout to one or more NSU or DDRMC. Or a N:1 topology, which is one or more NMUs to a single NSU or DDRMC. The path ownership (where QoS is set) is typically at the 'N' side of the INI path.This allows QoS to be set separately for each INI path.
INI connections have an advanced option parameter called 'ini strategy'. This parameter can be set to 'driver' or 'load'. When set to 'driver' the INI represents the NMU (the driver). When set to 'load' the INI represents the NSU or DDRMC (the load). In some cases this parameter can be set to 'auto' for inference by the tool, however in other cases it must be explicitly set. The path ownership is at the driver to load transition.
The INI supports the following use cases:
- Connect one or more AXI masters to multiple, independent DDRMCs
- In this use case, the AXI master is connected to an AXI NoC IP configured with one or more INI outputs. Each INI output is connected to another AXI NoC configured to include a DDRMC.
- Extend a NoC connection across levels of the design hierarchy
- In this use case, an AXI NoC in one level of hierarchy connects to an AXI NoC in another through INI ports at the hierarchy boundaries.