A Closer Look At Cobranet - Crown DriveCore I-Tech 4x3500 HD Operation Manual

I-Tech HD DriveCore Series Power Amplifiers

12.2 A Closer Look at CobraNet

Licensed by Cirrus, CobraNet is a protocol, firmware and hardware that lets you trans-
mit digital audio over a 100Base-T Fast-Ethernet network.
This section provides an overview of CobraNet. Cirrus Logic has provided a number of
technical papers that describe CobraNet in detail. These papers are available at:
http://www.cobranetinfo.com.
12.2.1 Fast Ethernet
(100Base-T)
Fast Ethernet (100Base-T) runs at 100Mbps (Megabits per second). It uses a hub or
network switch to interconnect all network nodes (components). This forms a star
network (see Figure 9.1). In a star network, all PCs are connected to a centralized hub
or switch. Messages are sent from the originating PC to the hub, which then transmits
the message either to the whole network or, if a switched hub (network switch) is used,
to the destination device only.
In larger Fast Ethernet networks, additional hubs, concentrators, and other network
hardware are used to form a larger network, as shown in Figure 12.4.
Figure 12.3 Star Topology
Today, commonly available networking cards are 10/100Base-T capable, which allows
them to be used on either 10BaseT or 100Base-T networks.
The maximum length of cable for CobraNet is the same as for Ethernet:100 meters over
CAT-5 copper cable, 2 kilometers over multimode fiber. Proprietary "Fast Ethernet via
single mode fiber" networks can reach even further.
12.2.2 Audio Specs
Sample rate: CobraNet can handle sample rates of 48 kHz or 96 kHz. I-Tech HD is
switchable between 48 kHz and 96 kHz.
Bit depth: Set each channel to transmit 16-, 20- or 24-bit audio data as desired.
Latency: The transmitter and receiver buffers required for reliable transmission are
set to 256 samples as a default. This gives a network transmission latency of 5.333 mS
(256 samples at 1/48 kHz per sample). I-Tech HD latency is switchable between 1.33,
2.66, and 5.33 mS.
12.2.3 Bundles and Audio Channels
You assign all audio channels to groups called Bundles for transmission over the
CobraNet network. Bundles were formerly called Network Channels.
A bundle can carry up to 8 audio channels. Up to 8 bundles can be sent in a 100 Mbps
line, depending on the signal's bit depth and sampling rate. Only 4 bundles are avail-
able when 96 kHz sampling rate is in use.
Figure 12.4 Multi-Star Topology
The usual assignment is 8 channels at 20 bits. You can use fewer channels per bundle,
but maximum size bundles are suggested for the most efficient use of network band-
width. If 24-bit data is desired, then only 7 audio channels can be loaded into a single
Bundle. With a 96 kHz sample rate, only 4 channels of audio are available.
Operation Manual
page 54