Mastership; Fault Tolerance - Crown 2/300 Operation Manual

Mastership

The BLU link bus requires one device on the bus to act as master. The master will provide the clock for all other devices on the bus. This means that the
whole bus is synchronised to a single audio clock.
NOTE: The BLU link sample rate for all device's on a BLU link bus must be configured to match. By default, the CDi DriveCore amps are configured with
the BLU link sample rate set to 96kHz.
In certain cases, it is possible to incorporate devices of more than one Ethernet transport type (i.e., AVB, CobraNet™, or Dante™) connected within the
same BLU link system. In other words, if you're careful, you can design a Harman system which actually includes two or more transports. For example,
it's possible for a Harman system to have CobraNet audio being converted to BLU link audio (BLU-800 and BLU-320 both have the ability to "bridge"
CobraNet to/from BLU link), which is then converted to Dante audio (BLU-806 and BLU-326 both have the ability to "bridge" BLU link to/from Dante). It all
depends on a given transport's ability to "slave" (AKA "re-clock") to a clock being generated by a separate transport.
Which transports support "slaving" to the clock of another transport?
Transport
AVB
BLU link
CobraNet
Dante
The previous table has critical implications on system design when combining two or more transports. Any system based on Soundweb London (including
Architectural Media Systems) supports the multi-transport combinations shown in the following table.
Combined Transports
BLU link + AVB
BLU link + CobraNet
BLU link + Dante
BLU link + Dante + AVB
Any multi-transport combination NOT specifically listed in the previous table is not allowed in Soundweb London systems (without being forced to use
analog interconnects between transports). For example, BLU link + AVB + CobraNet is NOT allowed, because the AVB and CobraNet networks would each
be synced to different clocks — their own.
Mastership is negotiated between all devices on the BLU link bus, and any change to the bus will trigger the negotiation to restart. The following rules
determine which device on the BLU link bus will become clock master:
• If there is only one BLU link device connected to CobraNet/AVB then that device is master.
• If there are multiple BLU link devices connected to CobraNet/AVB, then they compare master priorities.
• If there are multiple BLU link devices on CobraNet/AVB with the same highest priority, then they use MAC address to decide which is master.
• If there are no BLU link devices connected to CobraNet/AVB, then they first compare master priorities. Next, if the priorities are the same, they compare
MAC addresses.

Fault Tolerance

When the last BLU link device in a system is connected back to the first, the BLU link bus is capable of a degree of fault tolerance since each device
receives the same audio from two other devices. If a single cable connection is broken, the devices which are no longer connected will detect the cable
break: one device will detect that its BLU link in port is disconnected and the other will detect that its out port is disconnected. The devices will then re-
route the audio so that it can again pass through the bus.
NOTE: When the cable is broken, the audio will take longer to reach its destination. This added delay is not compensated for in any way, but is a side-
effect of the way the fault tolerance system functions.
CDi DriveCore Series Operation Manual
Supports Slaving to Another Transport
No
Yes
No
Yes
Clock Master
AVB provides the clock
CobraNet provides the clock
Either BLU link or Dante provides the clock
AVB provides the clock
Using BLU link
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