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3-5
Operation
DC/DC Converter
The DC/DC converter converts the 48 VDC on the system power bus to the
necessary operating voltages for its host network services module. The diagnostic
controller monitors and controls the operation of the DC/DC converter.
INB Interface
The INB Backplane is designed to transport fixed length data blocks between
modules in the SmartSwitch 9000 using an INB Time Division Multiplexing
(ITDM) design. The SmartSwitch 9000 INB bus delivers 2.0 Gbps of true data
bandwidth with all control and management communication being serviced on
the 8 bit out-of-band bus. The time slices of the INB manager operates in all three
modes at once, without user intervention.
Arbitration for the backplane is accomplished in the INB Time Division
Multiplexing (ITDM) logic. The arbitration is a three-level scheme that ensures
that no one can get the backplane for more than one time slice at a time.
The ITDM RAM contains 256 4-bit locations. This RAM is used to hold slot
numbers of modules participating in INB backplane arbitration. The arbitration
engine accesses this RAM once every time slice to get a slot number. That slot
number will be granted access on the next time slice if it is requesting. The
arbitration engine is always one time slice ahead, meaning that the value read
from the RAM is for the next time slice, not the current time slice.
The RAM is programmed on system power-up or when ever a module is
inserted/removed from the SmartSwitch 9000 chassis. There is a module
discovery program running that will detect these events. The amount of RAM to
be used and the position of the slot numbers in the RAM is determined by a
higher level system management program.
ITDM Arbitration levels
The three levels of arbitration guarantee that a module will get its allocated
bandwidth plus some more depending on what levels of arbitration it is
participating in.
ITDM RAM Allocation (Level 1)
This level guarantees access to the backplane. When a module requests access to
the backplane, it will get access to it when it's slot number is placed onto the bus.
This will ensure predicted or predetermined access to the backplane.