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Configure the Reference Clock Access and Configuration
PMC-CGM Installation and Use (6806800D53C)
41
4.4.7 Configure the Reference Clock
You can define the reference clock source, the frequency and the priority of the reference clock
inputs. For a description of the respective MIB objects refer to Table "cgmInputTable" on page
47.
Reference clock sources are:
z BITS interface 1 (input 3, frequency automatically configured via interface mode)
z BITS interface 2 (input 4, frequency automatically configured via interface mode)
z Linecard reference clcok A (input 7)
z Linecard reference clock B (input 12)
For the slave, the reference clock is always the Master/Slave synchronization clock. This is
automatically configured.
When you initially assign priorities, we recommend to start with the highest priority input.
Otherwise, the PLL may switch inputs unnecessarily or end up locked on a low-priority input
while a higher priority input is also valid.
If you want to change the selected PLL input by changing the priority, you have to change to
revertive mode first (cgmProtectionRevertiveModeState OID:.1.3.6.1.4.1.3656.8152.1.1.18.0).
Configuring the reference clock source for the T0/T4 path
To configure the reference clock, proceed as follows:
1. Start SNMP manager or MIB browser.
2. Connect to the PMC-CGM using one of its IP addresses.
3. Go to cgmInputFrequency object OID:.1.3.6.1.4.1.3656.8152.1.1.1.1.3.<instance
number which is equal to input number -1>.
4. Select the desired input frequency.
The following values are possible:
0: 8 KHz
1: 1544 KHz / 2048 KHz, depending on E1/T1 operation.
3: 19.44 MHz
5. Go to cgmT0InputPrioritiy object OID:.1.3.6.1.4.1.3656.8152.1.1.1.1.4.<instance
number which is equal to input number -1>.
6. Select the desired input priority.
A priority value from 2 to 15 is used by the T0 PLL to select an input. A lower
numerical value means a higher priority. A value of 0 disables the input, that means
it will not be selected as reference clock. A value of 1 cannot be set as it is used for
the master/slave synchronization clock.
Default value is 0.
This setting is applied to the protection partner as well.