PM8621-BI PMC-Sierra, Inc., PM8621-BI Datasheet - Page 33

• 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
Working and Protection Fabric
Figure 10 shows a working NSE-20G fabric with 32 SBSLITEs protected by another NSE-20G
device. The traffic can be selected to be using the working or protect LVDS links on the
SBS/SBSLITE devices. This is to protect against any hardware failure that may occur in the
fabric card. The switching over to the protect fabric card is easily achieved by one of the
following options: (a) software control, or (b) hardware control via the RWSEL pin. In either
case, user is responsible for synchronizing the connection pages between the working and the
protect fabric cards.
Standard and Doubled Fabric
Our discussion has so far been limited to standard fabric only. A limitation with the standard
fabric is its ability to handle multicasting without blocking. This limitation can be partially
(guaranteed non-blocking for 2:1 casts) alleviated by introducing more SBS or NSE devices to
the fabric. This is sometimes referred to as fabric “speed-up”.
Figure 11 shows a doubled SBS fabric. In this configuration, SBS devices are doubled up to
provide twice the number of timeslots available in a standard fabric. Each SBS pair has an
external multiplexer attached on the egress side to control the traffic selection. Traffic is either
selected from the “A” device or the “B” device at anytime depending on the control signal of the
multiplexer. The control signal is one of the TeleCombus signals from the “A” SBS device.
Depending on the path termination mode (MST, LPT, or HPT) employed by the system, different
TeleCombus signal is used for the multiplexer control. If the system is configured to run in either
MST or HPT mode, the OPL signal should be employed; otherwise, the OTAIS signal should be
used. User determines which control signal, OPL or OTAIS, when initializing the CSD via the
MIV. Please note that the OPL signal is shown in the figure. For a more in depth discussion on
doubled fabric, please refer to the “CHESS-NB Designing a Non-blocking Fabric for 1:2
Multicast (PMC-2020050).
Figure 12 shows a doubled SBS and NSE fabric. It is designed to circumvent the reduced
bandwidth supported by a doubled SBS fabric. Since the SBS devices are doubled up in a
doubled SBS fabric, the overall aggregate bandwidth is halved. The doubled SBS and NSE fabric
reclaims the lost bandwidth in a doubled SBS fabric.
Narrowband Chipset Device Driver Manual
Narrowband Chipset Overview
33