PM8611-BIAP PMC [PMC-Sierra, Inc], PM8611-BIAP Datasheet - Page 50

• Manufacturer Part Number: PM8611-BIAP
• Manufacturer: PMC [PMC-Sierra, Inc]

10.1.10 Transparent VT2/TU12 Mapping
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-2010883, Issue 2
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VT2 and TU12 virtual tributaries, TVT2s, are transported across the SBI bus in a similar manner
to the E1 tributary mapping. Table 18 shows the transparent structure where “I” is used to
indicate information bytes. There are two options when carrying virtual tributaries on the SBI
bus, the primary difference being how the floating V5 payload is located.
The first option is locked TVT mode that carries the entire VT2/TU12 virtual tributary indicated
by the shaded region in Table 18. Locked is used to indicate that the location of the V1,V2 pointer
is locked. The virtual tributary must have a valid V1,V2 pointer to locate the V5 payload. In this
mode the V5 indicator and payload signals, IV5, OV5, IPL and OPL, are optionally generated but
must be ignored by the receiving device. In locked mode timing is always sourced by the
transmitting side, therefore justification requests are not used and the JUST_REQ signal is
ignored. Other than the V1 and V2 octets which are carrying valid pointers, all octets can carry
data in any format. The location of the V1,V2,V3 and V4 octets is fixed to the locations shown in
Table 18.
The second option is floating TVT mode that carries the payload comprised of the V5 and I octets
within the shaded region of Table 18. In this mode the V1,V2 pointers are still in a fixed location
and may be valid but are ignored by the receiving device. The V5 indicator and payload signals,
IV5, OV5, IPL and OPL, must be valid and are used to locate the floating payload. The
justification request signal can be used to control the timing on the add bus. The V3 octet is used
to accommodate justification requests. The location of the V1,V2,V3 and V4 octets is fixed to the
locations shown in Table 18.
Table 18 Transparent VT2/TU12 Format
COL #
1-18
Unused
Unused
Unused
Unused
Unused
Unused
Unused
Unused
Unused
Unused
Unused
Unused
Unused
Unused
Unused
Unused
E1#1,1
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V1
I
I
I
I
I
I
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I
V2
I
I
I
I
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I
#2,1-3,21 E1#1,1
20-81
V1
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V2
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82
V5
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
#2,1-3,21 E1#1,1
83-144
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SBSLITE™ Telecom Standard Product Data Sheet
145
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I
#2,1-3,21 E1#1,1
146-207 208
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Preliminary
#2,1-3,21
209-270
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