PM8621-BI PMC-Sierra, Inc., PM8621-BI Datasheet - Page 37

• Manufacturer Part Number: PM8621-BI
• Description: Driver, NSE/SBS Narrowband Chipset Driver
• Manufacturer: PMC-Sierra, Inc.

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-2021248, Issue 1
SBS Egress Bus Integrity
Egress bus integrity on SBS has to be preserved at all time or the operation of downstream
devices can be adversely affected. Egress bus integrity includes the proper setup of all the
transport overhead (TOH), J1, stuff, V1/2/3/4/5 and the payload columns/bytes in the frame that
are vital to the well being of the bus signals. For example, improper bus signals can be generated
as a result of a misplaced J1 byte in the outgoing bus. Leveraging the MSU programming
capability on the egress side (applicable only to SBS revision B or later devices), the CSD
automatically handles all the bus integrity issues by fixing up all the bus-related columns/bytes.
This is done when virtual tributaries (VTs) or DS0s are setup using
nbcsFmgtMapDs0.
columns/bytes can be setup in advance before any VT/DS0 connections are setup. The advantage
is to reduce the connection time because these special columns/bytes are only setup once. Aside
from disconnecting a valid circuit, API
used to setup these special columns/bytes in advance. The connection map settings can then be
retrieved/populated by
“unused” DS0s or tributaries so that they have proper egress bus signal for the downstream
device. Extreme care should be taken on handling the unused DS0s (inside a tributary) or
tributaries (inside a SPE). Without unmapping the “unused” DS0s/tributaries, they may
inadvertently draw input from undesirable input timeslots and affect the egress bus signal.
It is noteworthy to point out that, once the payload types are defined, these
nbcsFmgtGetChgMap.
nbcsFmgtUnMapTrib
This unmapping is important to define the
Narrowband Chipset Device Driver Manual
and
nbcsFmgtMapTrib
nbcsFmgtUnMapDs0
Narrowband Chipset Overview
or
can be
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