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PRELIMINARY
XRT79L71
60
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
Figure 17 presents an illustration of two DS3 Boards that are connected to each other via a System Back-
Plane. Each of these DS3 Boards contains a Receive DS3 Framer and a Transmit DS3 Framer entity. In this
system, a given Receive DS3 Framer will receive and do performance monitoring (e.g., compute and verify
both the P and CP bits) on a given DS3 signal that it has received from a given Source Terminal Equipment.
After this incoming DS3 signal has passed through the Receive DS3 Framer it will then pass through the
System Back-plane and will arrive at the Transmit DS3 Framer on the other board. The Transmit DS3 Framer
will accept this DS3 data-stream and will process this DS3 data-stream by re-computing and inserting the DS3
overhead bits within DS3 data-stream.
NOTE: As this Transmit DS3 Framer re-computes and inserts the DS3 overhead bits back into this outbound DS3 data-
stream, it is imperative that this Transmit DS3 Framer NOT re-compute or potentially alter the state of the CP-bits.
Once the CP-bits are computed and inserted into an outbound DS3 data-stream, by the Source Terminal
Equipment, these CP-bit values must be retained as the DS3 data-stream traverses the network until it reaches the
Sink Terminal Equipment.
After this DS3 data-stream has passed through the Transmit DS3 Framer it will then be output to a remote Sink
Terminal Equipment.
In summary, the role of the Receive DS3 Framer within the Mid-Network Terminal is listed below.
To compute and verify the P-bits of each incoming DS3 frame
To compute and verify the CP-bits of each incoming DS3 frame
To output both payload and overhead bits to the System Back-Plane for transmission to the other board
within the Mid-Network Terminal Equipment.
Further, in summary, the role of the Transmit DS3 Framer within the Mid-Network Terminal is listed below.
FIGURE 17. A SIMPLE ILLUSTRATION OF AN EXAMPLE OF A MID-NETWORK TERMINAL EQUIPMENT
Receive DS3
Framer
Receive DS3
Framer
Transmit DS3
Framer
Transmit DS3
Framer
Receive DS3
Framer
Receive DS3
Framer
Transmit DS3
Framer
Transmit DS3
Framer
Incoming DS3 signal
From “Source” Terminal
Equipment
Outbound DS3 signal
To “Sink” Terminal
Equipment
Incoming DS3 signal
From “Source” Terminal
Equipment
Outbound DS3 signal
To “Sink” Terminal
Equipment
System Back-
Plane