Cirrus Logic Bundle Assignments in CobraNet Systems User Manual

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White Paper

Bundle Assignments in CobraNet

Systems

Ray Rayburn, Cirrus Logic, Inc.

Within a CobraNet

network, all audio channels are packaged into groups called Bundles (formerly called

Network Channels) for transmission. The default bundle configuration uses 8 audio channels of 20 bit
sample size. 8 audio channels per bundle is the maximum size possible, although using fewer audio
channels is permitted. For most efficient utilization of network bandwidth, use of maximum size Bundles is
suggested when possible. In the rest of this document we will be talking about maximum size Bundles.
Other bundle configurations are also possible which use 16 or 24 bit samples. When 24 bit audio channels
are used with a sample rate of 48-kHz, only 7 audio channels can be packaged into a single bundle due to
packet size limitations imposed by the Ethernet standard.

A CobraNet

network is coordinated by one of the devices operating in the role of conductor. When two

or more CobraNet

devices are interconnected properly, one of the devices will be automatically elected

the network conductor based on a priority scheme. The Conductor indicator will light on the CobraNet

device that is serving as the conductor.

Each CobraNet

device has the ability to send and receive a fixed number of Bundles. The Bundle number

tells the CobraNet

conductor which specific CobraNet

device is trying to communicate with which

other CobraNet

device(s) over the network. Use of Bundle numbers removes the necessity of the user

having to tell the devices the Ethernet hardware addresses of the other devices with which it is trying to
communicate. As long as the CobraNet

devices are all set to the same Bundle number, the CobraNet

system takes care of all the rest of the technical details of setting up an audio path over Ethernet between
the devices.

A given Bundle may have only one transmitter that places it onto the network. Unicast Bundles may have
only a single receiver. Multicast Bundles may have multiple receivers.

Ethernet networks can be built using either repeater hubs or switching hubs. A repeater is a half duplex
device which takes the data that comes into each port, and sends it back out all ports except the port in
came in on. A switch is a full duplex device which accepts data coming in each port and stores it until it can
examine the addressing of each packet of data. If the incoming data has a multicast destination address, it
then sends the data out all ports except the one it came in on. If, however, the data has a specific destination
address the switch only sends it out the port which is connected to the matching address. In an ordinary
Ethernet data network it is possible to mix both types of devices and have the network continue to work.
This is not the case with CobraNet

A CobraNet

network requires use of either all repeaters or all

switches. However, non-CobraNet

devices may be attached to a switched CobraNet

network via a

repeater.

On a repeater (hub based) network, there is a fixed maximum of 8 Bundles per network. Any Bundle may
be placed onto the network from any port, and will appear at every other port on the network. The Bundles
usually used in a repeater network are numbered in the range from 1 to 255, and are called Multicast
Bundles. Such channels are always transmitted in a multicast mode, and may be received by any of the
CobraNet

devices on the network.

As long as the limit of 8 total Bundles is not exceeded, it does not matter which channel numbers in the
range of 1 to 65,279 are used.

Use of switched hubs (or switches) is recommended when mixing computer data and CobraNet

on the

same network. Use of repeater hubs is strongly discouraged as audio dropouts may occur.

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