6.4.6. Configuring Clocking

This step is for users in the following categories:

• Map File: all SCX users
• Data Streaming: all SCX users

For more information about user categories, see Section 6.2, Determining Installation Requirements.

When the SCX160 SCxbus Adapter configuration program completes, the DCM Main Window appears. (For more information about the DCM Main Window, see Figure 8, DCM Main Window). At this time, you can set the configuration parameters that determine the clocking configuration for the multi-node system.

The clocking parameters you need to set are:

• SCxClockMode: this parameter determines whether the SCX160 SCxbus Adapter in a given node functions as the Slave, Master, or Fallback Master.
• SCxClockReference: this parameter is used only when the SCxClockMode parameter for the node is set to Master or Fallback Master. It indicates what clocking source the SCX160 SCxbus Adapter will use to drive clocking for the SCxbus. The possible sources are the SCX160 SCxbus Adapter's internal clock, the SCbus, or the SCxbus clock.
• SCbusClockMaster: this parameter indicates the board ID of the board that serves as the SCbus clock master. All other boards on the SCbus derive clocking from this board through the SCbus.
• SCbusClockMasterSource: this parameter indicates the source from which the SCbus clock master derives clocking, whether from the board's digital network interface, or from its internal clock.

Refer to the Node Configuration Chart you completed in Section 6.2.2, Analyzing Node Configuration Requirements to determine how to configure the clocking configuration for the multi-node system.

At system initialization, the SCxbus interface of the SCX160 SCxbus Adapter defaults to slave mode, thus initially the SCxbus is NOT clocked and the nodes cannot communicate with one another.

If the Master Clock node is not set up at system initialization, then the application must set up SCX160 SCxbus Adapter clocking by designating an SCxbus Master Clock node, an SCxbus Fallback Clock node, and a clock reference for each SCX160 SCxbus Adapter. The application can also change the SCbus interface clock mode of the SCX160 SCxbus Adapter. See the SCX160 SCxbus Adapter User's Guide for clocking and programming information required when developing application programs.

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