Using XDAB to share DSP resources

Clusters of NIONs can be interconnected in an XDAB ring, allowing up to 512 channels of redundant, low-latency audio to be exchanged. Wiring devices together in this way allows available DSP processing capacity to be shared between the group.

Note: The maximum channel count scales proportionally to the chosen sample rate. At a 48KHz sampling rate, 448 channels of audio can be exchanged.

Each NION has two XDAB ports, marked IN and OUT, which are used to physically wire them together in a ring using shielded CAT-6 cabling. The order of the NIONs in the ring is not important, since it is determined, and adjusted for, when the associated NWare project is deployed. However, NIONs that are specified as members of the same XDAB ring must be physically connected, otherwise each unit will indicate that a fault has occurred.

When the project is emulated or deployed, devices are not automatically distributed between the available DSPs in all the connected NioNodes. This has two important implications:

• Since a project can contain multiple XDAB clusters, as well as isolated NioNodes that are not in a cluster (perhaps connected via CobraNet), the designer must indicate to the compiler which NioNodes in the project are connected together via XDAB by adding an XDAB device to the project and wiring it to devices.
• The designer must specify in which role each of the DSP devices resides.

  Note: The compiler does not automatically allocate DSP devices in the project to DSP chips within each NioNode.