M160 Internet Router Hardware Guide
Figure 89: Connecting Fiber-Optic Cable to a PIC
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Replacing a PCG
During normal operation, both PCGs generate a 125- MHz clock signal, but only
one is designated as the master. The mo dules and ASICs in the Packet Forwarding
Enginethatusetheclocksignaltogatepacketprocessinguseonlythesignalfrom
the master PCG. For information about determining which PCG is the ma ster,see
“Maintaining the PCGs” on page 135.
PCGs are hot-pluggable,as described in Field-Replaceable Units (FRUs) on page
4. Removal or failure of the backup PCGdoes not affect router function. If the
master PCG fails or is removed from the chassis, however, the Packet Forwarding
Engine resets so that the componentsstart using the signal from the other PCG
(which becomes themaster). Packetforwarding halts while there isno clock signal,
because the Packet Forwarding Engine does not accept incoming packets.
To replacea PCG, perform the following procedures:
Removing a PCG on page 176
Installing a PCG on page 178
Removing a PCG
To removea PCG, follow this procedure (see Figure 90):
1. Place an electrostatic bag or antistatic mat on a flat, stable surface.
2. Attach an electrostatic discharge (ESD) grounding strap to your bare wris t and
connect the strap toone of the ESD points on the chassis. Make sure the router
is attached to a proper earth ground. For more information about ESD, see
“Preventing ElectrostaticDischarge Damage” on page 226.
176 Replacing Packet Forwarding Engine Components