Cirrus Logic CobraNet Audio Routing Primer - Manual (Page 3)

Bundle to Audio Routing Channel Mapping – txSubMap and rxSubMap
The RxSubMap and TxSubMap variable arrays are used to map Audio Routing Channels to and from Bundle
sub-channels. As described above, an Audio Routing Channel can be thought of as assigned to a specific time
slice within a Synchronous Serial Interface. Therefore, assigning an Audio Routing Channel to a bundle sub-
channel is equivalent to assigning an SSI time slice to a bundle sub-channel. See Appendix B for default SSI
to Audio Routing channel assignments.
Routing Variables
• txBundle *1 - Each transmitter has a txBundle variable associated with it which specifies the Bundle
Number assigned to that transmitter. There is one instance of this variable for each transmitter.
• rxBundle *1 - Each receiver has an rxBundle variable associated with it which specifies the Bundle
Number assigned to that receiver. There is one instance of this variable for each receiver.
• txSubMap * 2 - Each transmitter has up to 8 txSubMap variables associated with it. * 3
• rxSubMap * 2 - Each receiver has up to 8 rxSubMap variables associated with it. * 3
• txSubFormat * 2 - Each transmitter has up to 8 txSubFormat variables associated with it. * 3
• rxSubFormat * 2 - Each receiver has up to 8 rxSubFormat variables associated with it. * 3
• Each interface has one modeRateControl variable which specifies the latency and sample rate used
for all bundles transmitted and received by the interface.
*1 Array variables. There is one instance of this variable for each transmitter and each receiver.
*2 Array variables that are also members of an array. There are multiple instances of this variable for
each transmitter and each receiver.
*3 8 equals the maximum permissible number of audio sub-channels per bundle.
Putting it Together
To route audio between two CobraNet TM interfaces, both the transmitter and receiver must be configured to
send and receive audio channels. In many cases default values can be used and only txSubMap, rxSubMap,
txBundle and rxBundle variables need be set.
Transmitter Configuration
• Assign a bundle number to the transmitter using txBundle.
• Assign Audio Routing channels (and by extension SSI audio channels) to the transmitter (Bundle)
using txSubMap.
• Specify the format of the channels using txSubFormat
• Make sure the value of modeRateControl agrees with the selected txSubFormat.
• Make sure txSubCount for each transmitter is greater than or equal to the number of channels being
transmitted in the bundle. If the value of txSubCount is larger than required, unassigned sub-
channels will be sent as empty channels.
Receiver Configuration
• Assign a bundle number to a receiver using rxBundle.
• Assign Audio Routing channels (and by extension SSI audio channels) to the receiver (Bundle)
using rxSubMap
•
Make sure the value of modeRateControl agrees with the format of the channels to be received.
CobraNet TM Audio Routing Primer Rev. 1.2 ©Copyright 2004 Cirrus Logic, Inc
Page 3 of 9