CobraNet Hardware User’s Manual
Synchronization
DS651UM21
©
Copyright 2004 Cirrus Logic, Inc.
17
Version 2.1
The following synchronization modes are further described below:
•
•
"Internal Mode with External Sample Synchronization" on page 17
•
"External Word Clock Mode" on page 17
•
"External Master Clock Mode" on page 18
•
"External Master Clock Mode with External Sample Synchronization" 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 Internal Mode with External Sample Synchronization
This mode is identical to internal mode except that it allows synchronization of derived
clocks (sample clock, audio bit clock) to an external source via the reference clock input.
This additional functionality is useful when adapting the CobraNet interface to a device
that already has circuitry for generating those clocks.
Conductor—The VCXO is “parked” according to the
syncClockTrim
setting.
Performer—The VCXO is “steered” to match the clock transmitted by the conductor.
5.1.3 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
µ
s. 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.
