CobraNet Hardware User’s Manual
Synchronization
The following synchronization modes are further described below:
• "Internal Mode" on page 18
• "External Word Clock Mode" on page 18
• "External Master Clock Mode" on page 18
5.1.1 Internal Mode
All CobraNet clocks are derived from the onboard VCXO. The master clock generated by
the VCXO is available to external circuits via the master clock output.
Conductor—The VCXO is “parked” according to the syncClockTrim setting.
Performer—The VCXO is “steered” to match the clock transmitted by the Conductor.
5.1.2 External Word Clock Mode
All CobraNet clocks are derived from the onboard VCXO. The VCXO is steered from an
external clock supplied to the reference clock input. The clock supplied can be any
integral division of the sample clock in the range of 750Hz to 48kHz.
External synchronization lock range: 5 µs. This specification indicates drift or wander
between the supplied clock and the generated network clock at the conductor. Absolute
phase difference between the supplied reference clock and generated sample clock is
dependant on network topology.
Conductor—This mode gives a means for synchronizing an entire CobraNet network to
an external clock.
Performer—The interface disregards the fine timing information delivered over the
network from the conductor. Coarse timing information from the conductor is still used;
fine timing information is instead supplied by the reference clock. The external clock
source must be synchronous with the network conductor. This mode is useful in
installations where a house sync source is readily available.
5.1.3 External Master Clock Mode
The VCXO is disabled and MCLK_IN is used as the master clock for the node. This is a
“hard” synchronization mode. The supplied clock is used directly by the CobraNet
interface for all timing. This mode is primarily useful for devices with multiple CobraNet
interfaces sharing a common master audio clock. The supplied clock must be
24.576 MHz. The supplied clock must have a 37 ppm precision.
Conductor—The entire network is synchronized to the supplied master clock.
Performer—The node will initially lock to the network clock and will “jam sync” via the
supplied master clock. The external clock source must be synchronous with the network
conductor.
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©Copyright 2005 Cirrus Logic, Inc.
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