XR72L52 Datasheet, PDF (221/480 Pages) Exar Corporation – TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L52
REV. 1.0.1
FIGURE 71. 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 Line Card
The Receive WAN Interface line 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 Line Card
The Transmit WAN Interface Line Card receives the outbound DS3 data stream from the system back-plane.
As the Transmit WAN Interface Line Card 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 XRT72L52 Framer IC.
2. Compute the even-parity over all the payload 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 opposite edge of the wide-area-network, from the Source Termi-
nal Equipment) will receive and terminate this DS3 data stream. As the Sink Terminal Equipment receives this
DS3 data stream it will also do the following.
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
205