Below may help taken from CCO. It applies to 5400 as well.
dial-tdm-clock
To configure the clock source and priority of the clock source used by the time-division mulitiplexing (TDM) bus on the dial shelf of the Cisco AS5800, use the dial-tdm-clock global configuration command. To return the clock source and priority to the default values, use the no form of the command.
[no] dial-tdm-clock priority number {external {e1 | t1} [120ohm] | freerun | trunk-slot slot port port}
Syntax Description
priority number
Specify the priority of the clock source. The range is 1 to 50. Priority 1 is the highest priority and 50 is the lowest.
external
Specify the priority of an external clock source. The external clock source is connected to the front panel of the dial shelf controller (DSC) card.
{e1 | t1} [120ohm]
Specify priority of the E1 (2.048 MHz) or T1 (1.54 MHz) external clock source. The default value of the external coaxial cable impedance is 75 ohm. Specify the 120ohm option if a 120 ohm coaxial cable is connected.
freerun
Specify the priority of the local oscillator clock source.
trunk-slot slot
Specify the priority of the trunk card to provide the clock source. The slot number is from 0 to 5 (these are the only slots capable of providing clock sources).
port port
Specify the controller number on the trunk used to provide the clock source. The port number is from 0 to 28. The T1 and E1 trunk cards each have 12 ports. The T3 trunk card has 28 ports.
