[c-nsp] T1 Timing: Internal vs. Free Running

Bruce Pinsky bep at whack.org
Fri Jul 7 18:23:02 EDT 2006


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John Neiberger wrote:
> On a 2800/3800 ISR with Multiflex T1 modules, what is the difference
> between "clock source internal" and "clock source free-running" ?  It
> seems like they both tell the router to use an internal clock, but
> there must be more to it than that.
> 

A quick look at
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124tcr/tir_r/int_a1ht.htm#wp1202063

tells the difference.  Basically, internal uses a PLL driven oscillator on
the T1 controller whereas the free-running uses an oscillator on the
RP/motherboard (that presumably is not PLL'd).

- --
=========
bep

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