Maintenance Bus - Cisco GSR12/60 - 12012 Router -AnyLAN, SONET/SDH Installation And Configuration Manual

Maintenance Bus

The Cisco 12012 maintenance bus (MBus) and MBus modules manage all of the
maintenance functions of the system.
The Cisco 12012 MBus consists of two separate busses (providing MBus redundancy) that
link all of the line cards, the RP, the switch fabric cards, the power supplies, and the blower
modules. Each component contains an MBus module that allows the component to
communicate over the MBus. The MBus module on each component is powered by
+5 VDC directly from the power supply. The MBus modules perform the following
functions:
•
Power-up/down control—Each MBus module directly controls the DC-DC converters
on the component it is mounted on based on commands it receives from its on-board
EPROM and from the master RP. Each MBus module is tied directly to +5 VDC from
the power supply. When power is applied to the Cisco 12012, all MBus modules
immediately power up. The MBus modules on the RP or clock and scheduler card
immediately turn on the DC-DC converter, powering up the respective card. The line
card MBus module waits to power up the line card until it receives a command from the
master RP.
•
Device discovery—The RP can determine the system configuration using the MBus. A
message is sent from the RP over the MBus requesting all installed devices to identify
themselves. The response back provides slot number and card and component type.
•
Code download—A portion of the line card operating software can be downloaded from
the RP to the line card over the MBus. Because the MBus is relatively slow compared
to the switch fabric, only enough code is downloaded to the line card for it to access the
switch fabric and complete the download process.
•
Diagnostics—The diagnostic software image is downloaded from the RP to the card
under test.
Physical and Functional Overviews
Product Overview 1-39