# Clock Management EMC

When a board is started or Hot Swap inserted, the Clock Management EMC configures the clock on the board as specified in the NMS OAM database. During system initialization, the Clock Management EMC also verifies that the bus clock master board (the board driving the clock) is running before any clock slave boards start up.

The Clock Management EMC exists as a managed object within NMS OAM and has keywords. For a list of these keywords, refer to Clock Management EMC keyword summary.

The Clock Management EMC provides H.100 and H.110 bus clock management services to boards in a chassis that are connected through the bus. As each board starts up, applications registered for NMS OAM alert notification can receive the following clocking-related events:

Event | Description
--- | ---
CLKEVN_CONFIGURED | Board clock is successfully configured.
CLKEVN_INVALID_CONFIG_DATA | Board clock configuration is invalid or missing.
CLKEVN_CONFIG_FAILED | An attempt to configure board clock failed.
CLKEVN_OPEN_OAM_FAILED | An attempt to open a board plug-in failed.
CLKEVN_OPEN_SWITCH_FAILED | Could not open the board switch. If the first switch open attempt fails, a second attempt is made. It is possible for an application to receive CLKEVN_CONFIGURED after CLKEVN_OPEN_SWITCH_FAILED.

These events are received in the same manner as other NMS OAM events. For more information, see Event buffer management.

If clocking cannot be configured for a board, the board remains in standalone clock mode. In this mode, the board is not able to make connections to the CT bus.

## Board-level clock management architecture

The clock management component of NMS OAM consists of the following software modules:

Module | Description
clkmgr.emc | The NMS OAM interface to clock management. This EMC has a managed object in the NMS OAM database, which can be accessed by an application. For more information, see Clock Management EMC keyword summary.
cfbm.exe | The clock manager service. cfbm.exe is a Natural Access application that is started by clkmgr.emc. It is started as a service under Windows. It is started as a daemon under UNIX. To perform all of its clock management operations, cfbm.exe makes calls to the Natural Access Switching service (SWI).

The following illustration shows the clock management architecture: