XRT72L13 Datasheet, PDF (314/370 Pages) Exar Corporation – M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC

XRT72L13
M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC
REV. P1.0.6
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PRELIMINARY
NOTE: When the "Framing with Parity" option is selected,
the "Receive DS3 Framer" block will declared an "OOF"
condition if P-bit errors were detected in two out of 5 con-
secutive DS3 "M-frames".
3.3.2.6.2 CP-Bit Checking/Options
CP-bits are very similar to P-bits except for the follow-
ing.
1. CP-bits are used to permit performance monitor-
ing over an entire DS3 path (e.g., from the
“source” terminal); through any number of “mid-
network” terminals to the “sink” terminal).
2. P-bits are used to permit performance monitoring
of a DS3 data stream, as it is transmitted from
one terminal to an adjacent terminal.
How CP-Bits are Processed
The following section describes how the CP-bits are
processed at three locations.
• The “Source” Terminal Equipment
• The “Mid-Network” Terminal Equipment
• The “Sink” Terminal Equipment
Figure_62 presents a simple illustration of the loca-
tions of these three types of Terminal Equipment,
within the Wide-Area Network.
FIGURE 101. A SIMPLE ILLUSTRATION OF THE LOCATIONS OF THE “SOURCE”, “MID-NETWORK” AND “SINK” TERMI-
NAL EQUIPMENT (FOR CP-BIT PROCESSING)
CCuustsotmomerer
PPrermemisiese
EEqquuipipmmenent _t
SSoouurcrece
TTeremrmininaal _l
EEqquuipipmmenent _t
MMidid-N-Netewtwoorkrk
TTeremrmininalal
EEqquuipipmmenent _t
SSininkk
TTeremrmininaal _l
EEqquuipipmmenent _t
CCuustsotommerer
PPrermemisiese
EEqquuipipmmenent _t
The Wide Area Network
NOTE: The user of the terms “Source” and “Sink” Terminal
Equipment are used to simplify this discussion of CP-Bit
Processing. In reality, the “Source” Terminal Equipment (in
Figure_62) will also function as the “Sink” Terminal Equip-
ment (for DS3 traffic traveling in the opposite direction).
Likewise, the “Sink” Terminal Equipment (in Figure_62) will
also function as the “Source” Terminal Equipment.
Processing at the “Source” Terminal Equipment
The “Source” Terminal Equipment (located at one
edge of the wide-area network) will typically receive
its DS3 payload data from some Customer Premise
Equipment (CPE). As the “Source” Terminal Equip-
ment receives this data from the CPE, it will compute
the even-parity value over all bits within a given “out-
bound” DS3 frame. The Terminal Equipment will then
insert this even parity value into both of the P-bit
fields and both the CP-bits fields, within the very next
“outbound” DS3 frame.
Hence, both the P-bit values and CP-bit values will
originate at the “Source” Terminal Equipment.
Processing at the “Mid-Network” Terminal Equip-
ment
The “Mid-Network” Terminal Equipment has the task
of doing the following.
• Receiving a DS3 data stream, via the “Receive
WAN Interface” Line Card.
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