Cirrus Logic CobraNet - Manual (Page 122)

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Copyright 2006 Cirrus Logic, Inc. DS651PM25
CobraNet Programmer’s Reference
Recommended User Interface Practices
7. Recommended User Interface Practices
7.1 Channel Assignments and Labeling
There are at least five layers where audio channels are numbered:
• User labels on the back panel of a device.
• As synchronous serial time slot and interface assignments. This is determined
by how the audio I/O is physically connected and multiplexed.
• As audio buffer offsets within the CobraNet interface. There is a fixed mapping
between the time slot and interface assignments and the audio buffer offsets
for each basic CobraNet I/O configuration supported.
• As audio routing channels within the CobraNet interface. Valid routing channels
are in the range 1-64. Channel 0 is reserved to indicate an unused channel.
The mapping between I/O indices and audio buffer offsets is determined by the
audioMap MI variable.
• As bundle and audio channel assignments. Valid bundle numbers are 1-65535.
Bundle 0 indicates an unused transmitter or receiver. A bundle may carry up to
8 audio channels. Routing channels are assigned to bundles through the
txSubMap and rxSubMap MI variables.
7.1.1 Audio I/O Map
The audioMap variables may need to be set up by the manufacturer. Audio inputs starting
from the channel labeled 1 should be assigned starting at routing channel 1. Audio
outputs starting from the channel labeled 1 should be assigned starting at routing channel
33. The
audioMap values may be initialized through firmware customization or the HMI.
7.1.2 Bundle Assignments
It is recommended that all front panel interfaces allow selection of multicast bundles in the
range 1-255 and unicast bundles in the range 256-65279. We recommend against
allowing private bundle assignments from a front panel user interface since these are
conditioned on a 48-bit MAC address. Private bundle assignments are best left to a
central graphical user interface operating via SNMP.
Transmitters—Audio channels are transmitted in groups of up to 8 onto the network via a
bundle. It is an advisable policy to pack as many audio channels into a bundle as possible
as this improves network efficiency. This does strategey does not necessarily limit routing
flexibility as complex routing functionality can be readily accomplished at the receiver
side. At a minimum, user control of bundle assignments per network transmitter should be
provided. Optional user interface control of transmitter functionality may include any
combination of the following:
• Audio Resolution on a per-audio-channel Basis
• Audio Source Channel Mapping per Transmitter Audio Channel
• Number of Audio Channels to Include in Bundle Transmission
• Bundle and Request Priority
Receivers—The receiver can extract up to 8 audio channels from a bundle. The receiver
decodes the data according to the tags attached to the bundle by the transmitter. At a
minimum, user control of the bundle assignment per network receivers should be