XRT72L13 Datasheet, PDF (315/370 Pages) Exar Corporation – M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC

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PRELIMINARY
XRT72L13
M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC
REV. P1.0.6
• Transmitting this same DS3 data stream (out to
another Remote Terminal Equipment) via the
“Transmit WAN Interface” Line Card.
Figure 102 presents an illustration of the basic archi-
tecture of the “Mid-Network” Terminal Equipment.
FIGURE 102. ILLUSTRATION OF THE “PRESUMED CONFIGURATION” OF THE MID-NETWORK TERMINAL EQUIPMENT
System Back-plane
DS3 Traffic
from “Source”
Terminal
Equipment
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DS3 Traffic to
“Sink” Terminal
Equipment
The Mid-Network Terminal Equipment
Operation of the “Receive WAN Interface” Card
The “Receive WAN Interface” card receives a DS3
data stream from some remote Terminal Equipment.
As the “Receive WAN Interface” card does this, it will
also do the following:
1. Compute and verify the “P-Bits” of each
“inbound” DS3 frame.
2. Compute and verify the “CP-Bits” of each
“inbound” DS3 frame.
3. Output both the “payload” and “overhead” bits to
the system back-plane.
Operation of the “Transmit WAN Interface” Card
The “Transmit WAN Interface” Line Card receives the
“outbound” DS3 data stream from the system back-
plane. As the “Transmit WAN Interface” receives this
data it will also do the following.
1. Extract out the “CP-bit” values, from the “Receive
WAN Interface” line card (via the system back-
plane) and insert these values into the CP-bit
fields, within the “outbound” DS3 data stream; via
the “Transmit Overhead Data Input Interface”
block of the XRT72L13 Framer IC.
2. Compute the even-parity over all bits, within a
given “outbound” DS3 frame, and insert this value
into the “P” bits within the very next “outbound”
DS3 frame.
3. Transmit this resulting DS3 data stream to the
remote terminal equipment.
Processing at the “Sink” Terminal
The “Sink” Terminal Equipment (located at the oppo-
site edge of the wide-area-network, from the “Source”
Terminal Equipment) will receive and terminate this
DS3 data stream. As the “Sink” Terminal Equipment
receives this DS3 data stream; it will also do the fol-
lowing.
1. Compute and verify the “P”-bits within each
“inbound” DS3 frame.
2. Compute and verify the “CP” bits within each
“inbound” DS3 frame.
4.3.3 The Receive HDLC Controller Block
303