Manual

ManualsBrandsCirrus Logic ManualsHardwareCobraNet Audio Routing Primer

Components of Routing

Bundles

A Bundle is the basic unit of data for transporting audio over a CobraNet

network and can contain from

zero to eight audio sub-channels. Sample size, sample rate and transmission latency all have an impact on

processor bandwidth and packet sizes required to process and transmit the audio data. These factors can limit

the number of audio channels that can be processed by a CobraNet

interface. The maximum number of

audio sub-channels allowable per bundle will be from 3 to 8 depending on these settings. The maximum

number of bundles possible can also be affected by these settings. Maximum sub-channel count per bundle

will typically be eight but may be less depending on the particular configuration.

An important attribute of the Bundle is the identifying number assigned to it (the Bundle number). The

Bundle number determines both where the data is sent and, to a large extent, how it is sent. When a receiver

on one interface is assigned the same bundle number as that of a transmitter on another interface, the

CobraNet

protocol will automatically establish a connection and begin transmitting audio data between the

interfaces.

Bundles can be transmitted using the following modes:

• Unicast (one-to-one)

• Multiple unicast (up to four copies unicast to more than one receiver)

• Multicast (one bundle to an unlimited number of receivers)

• Private (same as unicast or multicast but requiring specification of a MAC address)

Refer to the Programmer’s reference for information on valid bundle numbers and how they affect addressing

modes.

Network Transmitters and Receivers

Transmitters and Receivers are logical entities within the CobraNet

interface which are closely coupled to

the concept of Bundles. Each transmitter or receiver is capable of sending or receiving one Bundle. The

number of transmitters and receivers within a CobraNet

interface is dependant on the particular

implementation and is fixed by the firmware. The user can configure the number of available transmitters or

receivers to be used.

Synchronous Serial Interface

Each CobraNet

interface contains one or more Synchronous Serial Interfaces, or SSI’s. SSI’s carry

multiplexed audio data into and out of the CobraNet

interface in time slices and are typically connected to

DACs, ADCs, DSP processors and other digital audio interfaces. See Appendix C for more information on

the SSI.

Audio Routing Channels

Audio routing channels are used to map audio data between a multiplexed SSI time slice and a bundle sub-

channel. CobraNet

interfaces contain up to 64 audio routing channels numbered from 1 to 64. Channels 1-

>32 are used for transmitting and channels 33->64 are used for receiving. The actual number of routing

channels available is dependant on the particular CobraNet

implementation. Channel 0 is an additional

special case which is, strictly speaking, not a routing channel. Channel 0, when assigned to a transmitter

Bundle, will cause transmission of an empty channel equivalent to silence. Channel 0, when assigned to a

receiver bundle sub-channel, will cause the bundle sub-channel received to be discarded.

For practical purposes, each unique audio routing channel can be thought of as having a fixed association

with a unique SSI time slice. In reality, audio routing channels are assigned to SSI time slices via the

audioMap variable array. Omission of this variable in Figure 1 is intentional. It should not be changed. See

Appendix B for default SSI to Audio Routing channel assignments.

CobraNet

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