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Configuring Timing (Clock) Signals
PA-4T+ Synchronous Serial Port Adapter Installation and Configuration8-10
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-config command (only the relevant output from the show
running-config command 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.