PM8621-BI PMC-Sierra, Inc., PM8621-BI Datasheet - Page 26

• 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
TeleCombus and SBI Bus Tributary Naming Convention
In SBI mode, the tributary payload type on the SBS has to be properly defined for the chipset to
function properly. SBI336 column multiplexed 4 SBI buses together. It complies with most of the
SBI bus specification. Each SBI bus consists of 3 SPEs and each SPE can consist of T1, E1,
TVT1.5, TVT2, DS3/E3, and fractional T1/E1 type payloads. Traffic type cannot be mixed within
one SPE but can be mixed independently across SPEs. For instance, the first SPE can carry 28
T1s (Note: T1 and TVT1.5 can be mixed within one SPE), the second SPE can carry 21 E1s and
the third can be defined for one DS3.
In either bus mode, the user specifies the VTs to be switched across the fabric. For instance, the
user need only specify the source and destination SBS, SBI bus number, SPE number, and the T1
number to route the entire T1 across the fabric. In TeleCombus mode, SONET specification is
used to label the virtual tributaries specified by the STS-3 (ranges from 1 to 4) and STS-1 (ranges
from 1 to 3) numbers, the VT group number ranges from 1 to 7, and the VTx number where x =
1.5, 2, 3, and 6. The tributary number for VT1.5, VT2, VT3, and VT6 varies from 1 to 4, 3, 2, and
1 respectively (Figure 4). Note that there can only be one type of VT defined in one particular VT
group.
SDH naming convention may also be employed in place of SONET. The AUG-1, AU-3, and
TUG-2 replace the STS-3, STS-1 and VT group numbers. The VTs are replaced by TU-11, TU-12
and TU-2 that correspond to the VT1.5, VT2, and VT6 in SONET (Note: There is no SDH
equivalent of SONET’s VT3). This naming convention applies to frames with AU-3 structure. For
AU-4 structured frame, all are the same except the TUG-3 number replaces the AU-3 number.
Table 3: SONET vs. SDH Virtual Tributary Naming Convention in TeleCombus
The API functions for status retrieval and PRGM refer to the STS-1 path number. The “order of
transmission” of the bytes in a SONET/SDH frame is followed and Table 4 provides the
translation between the tributary numbering and the STS-1 path number. It can also be interpreted
as how the columns from different STS-1 data streams are interleaved with each other. In other
words, the column of (1,1) is followed by that of (2,1), then the column of (3,1), and etc.
Table 4: TeleCombus and SBI336 Bus STS-1 Path Numbering
STS-3 number
STS-1 number
VT group number
Virtual Tributary number:
TeleCombus (STS3 num, STS1 num)
SBI336 Bus (SBI num, SPE num)
SONET
SDH AU-3 structured frame
AUG-1 number
AU-3 number
TUG-2 number
Tributary Unit (TU) number
STS-1 Path number
Narrowband Chipset Device Driver Manual
SDH AU-4 structured frame
AUG-1 number
TUG-3 number
TUG-2 number
Tributary Unit (TU) number
Narrowband Chipset Overview
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