4.2.  Designating Clock Modes

Clocking designations are determined by evaluating total system resources and the system configuration, including SCSA boards other than the SCX160 SCxbus Adapter installed in each node. For each node, you must determine whether the clock for a particular board will be the master clock source or slaved to a clock reference provided on the SCbus or the SCxbus.

The SCX160 SCxbus Adapter clock mode(s) must be determined independently for both the SCbus and the SCxbus interfaces.

The clock designations for the SCbus are as follows:

• Master clock mode: typically, a network interface board provides System Wide Clock Master (SWCM) that becomes the clock reference for all SCSA boards and the SCX160 SCxbus Adapter in that node.
• Fallback master clock mode: takes over as the master clock if the board operating in master clock mode fails.
• Slave mode: SCbus boards operating in this mode take master clock from the SCbus as their clock reference.

The clock designations for the SCxbus are as follows:

• Master clock mode: the SCX160 SCxbus Adapter operating in master clock mode provides master clock via Right SCxbus Clock to all other SCX160 SCxbus Adapters in the system via the SCxbus.
• Fallback master clock mode: the SCX160 SCxbus Adapter operating in fallback master clock mode provides fallback master clock via Left SCxbus Clock to all other SCX160 SCxbus Adapters in the system via the SCxbus.
• Slave mode: SCX160 SCxbus Adapters operating in this mode take master clock from the SCxbus to synchronize its SCxbus interface circuits.

Unless otherwise configured by the downloadable parameters file at Dialogic Service startup, the SCX160 SCxbus Adapter clocking defaults to the following:

• For the SCxbus interface, Slave state
• For the SCbus interface, Slave state
• For the default clock when clock is not available from one of the above, the local crystal oscillator

To enable communication between nodes, one node must be designated as the SCxbus master clock node. Clocking designations can be accomplished at Dialogic Service startup by modifying the downloadable parameter file as described in Appendix A - Downloadable Parameters. Otherwise, all clock modes must be set by issuing an scx_setbrdparm( ) function (see Chapter 6.  Function Reference). The application can change the clocking configuration during system operation.

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