Replacing A Pcg; Removing A Pcg; Figure 89: Connecting Fiber-Optic Cable To A Pic - Juniper Internet Router M160 Hardware Manual

M160 Internet Router Hardware Guide

Figure 89: Connecting Fiber-Optic Cable to a PIC

Replacing a PCG

During normal operation, both PCGs generate a 125-MHz clock signal, but only
one is designated as the master. The modules and ASICs in the Packet Forwarding
Engine that use the clock signal to gate packet processing use only the signal from
the master PCG. For information about determining which PCG is the master, 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 PCG does not affect router function. If the
master PCG fails or is removed from the chassis, however, the Packet Forwarding
Engine resets so that the components start using the signal from the other PCG
(which becomes the master). Packet forwarding halts while there is no clock signal,
because the Packet Forwarding Engine does not accept incoming packets.
To replace a PCG, perform the following procedures:

Removing a PCG

To remove a PCG, follow this procedure (see Figure 90):
1.
2.
176
Replacing Packet Forwarding Engine Components
Removing a PCG on page 176
Installing a PCG on page 178
Place an electrostatic bag or antistatic mat on a flat, stable surface.
Attach an electrostatic discharge (ESD) grounding strap to your bare wrist and
connect the strap to one 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 Electrostatic Discharge Damage" on page 226.