Cisco XR 12404 - Manual (Page 45)

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Cisco XR 12404 Router Installation Guide
OL-13830-02
Chapter 1 Cisco XR 12404 Router Overview
Maintenance Bus
Maintenance Bus
The Cisco XR 12404 router maintenance bus and MBus modules manage all of
the maintenance functions of the system. The MBus consists of two separate
busses (providing MBus redundancy). Each MBus is linked to all of the following.
• Line cards
• Route Processor
• CSF card
The MBus module located on each component, communicates over the MBus and
is powered by +5 VDC directly from the fabric card. The MBus performs the
functions of power-on/off control for each component, component (device)
discovery, code download, diagnostics, and environmental monitoring and
alarms.
Power-On/Off Control
Each MBus module directly controls the DC-to-DC converters on the component
it is mounted on based on commands the component receives from its on-board
EPROM and from the route processor. Each MBus module is tied directly to
+5 VDC from the consolidated fabric card.
When power is applied to the Cisco XR 12404 router, all MBus modules
immediately power on. The MBus modules on the route processor and CSF card
immediately turn on the DC-to-DC converter, powering up the respective card.
The line card MBus module waits to power on the line card until it receives a
command from the route processor.
Component Discovery
The route processor can determine the system configuration using the MBus. A
message is sent from the route processor over the MBus requesting all installed
devices to identify themselves. The response back provides component type, line
card slot number, and CSF card slot number.
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