Configuring Timing (Clock) Signals

Note Cisco IOS Release 11.2(7a)P or later, or 11.1(10)CA or later loaded on your Cisco 7200 series, Cisco 7000 series, or Cisco 7500 series router with a VIP2-40(=) support nonstandard clock rates (any value from 1200 to 8000000) on PA-4T+ interfaces.

Cisco IOS Release 12.0(3)T or later, or 12.0(1)XE or later support nonstandard clock rates on PA-4T+ interfaces installed in Cisco 7204VXR and Cisco 7206VXR routers.

Cisco IOS Release 11.3(6)NA or later loaded on your Cisco uBR7200 series router supports nonstandard clock rates (any value from 1200 to 8000000) on PA-4T+ interfaces.

Nonstandard clock rates are rounded (if necessary) to the nearest clock rate that the hardware can support

The following example shows how to configure a nonstandard clock rate on a PA-4T+ interface in port adapter slot 1 (1/0) on a Cisco 7200 series, Cisco uBR7200 series, or Cisco 7100 series router:

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z. Router(config)# interface serial 1/0

Router(config-if)# clock rate 1234567

%Clockrate rounded to nearest value that your hardware can support. %Use Exec Command ‘show running-config’ to see the value rounded to. Router(config-if)# exit

Router(config)#

The following example shows how to configure a nonstandard clock rate on a PA-4T+ interface in interface processor slot 3 (3/1/0) on a VIP2:

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z. Router(config)# interface serial 3/1/0 Router(config-if)# clock rate 1234567

%Clockrate rounded to nearest value that your hardware can support. %Use Exec Command ‘show running-config’ to see the value rounded to. Router(config-if)# exit

Router(config)#

The following example shows how to determine the exact clock rate that the interface was rounded to by using the show running-configcommand (only the relevant output from the show running-configcommand is included in the example; other information has been omitted).

Router# show running-config

Building configuration...

...

!

interface Serial 1/0

no ip address

clockrate 1151526

!

...

Inverting the Clock Signal

Systems that use long cables or cables that are not transmitting the TxC (clock) signal might experience high error rates when operating at higher transmission speeds. If a PA-4T+ DCE port is reporting a high number of error packets, a phase shift might be the problem. Inverting the clock might correct this shift.

8-10PA-4T+ Synchronous Serial Port Adapter Installation and Configuration

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Cisco Systems PA-4T manual Inverting the Clock Signal