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PRELIMINARY
XRT79L71
64
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
F-Frame # 4 consists of 3 bit fields for the FEBE (Far-End Block Error) channel. If the Near-End XRT79L71
detects CP-bit errors or a framing bit error within the incoming (received) DS3 data-stream, then it will inform
the remote terminal of this fact by setting the three FEBE bits within the outgoing, or return DS3 frame, to any
pattern other than [1, 1, 1] to indicate an erred condition. The Transmit Section of the XRT79L71 will typically
set the FEBE bits to the value [1, 1, 1] in order to denote an un-erred condition, only if both of the following
conditions are true.
The XRT79L71 has not detected any M-bit or F-bit errors within its incoming (received) DS3 data-stream
The XRT79L71 has not detected any CP-bit errors within its incoming (received) DS3 data-stream
This concept of transmitting the FEBE indicator in response to these error conditions is reinforced in Figure 20 Figure 20 presents an illustration of a given Near-End Terminal that is exchanging DS3 data with the remote
terminal, in an un-erred manner.
In response to this un-erred condition, the Transmit DS3 Framer within the Near-End Terminal will respond by
setting each of the three (3) FEBE bit-fields to "1". Figure 21 presents an illustration of the Transmit DS3
Framer sending this un-erred indication to the Remote Terminal Equipment.
Next, Figure 22 presents an illustration of a given Near-End Terminal that is detecting framing (F-bit) errors
within its incoming DS3 signal.
FIGURE 20. A SIMPLE ILLUSTRATION OF A NEAR-END TERMINAL EXCHANGING DS3 DATA WITH A REMOTE TERMI-
NAL
, IN AN UN-ERRED MANNER
FIGURE 21. A SIMPLE ILLUSTRATION OF THE NEAR-END TERMINAL TRANSMITTING THE UN-ERRED INDICATION TO
THE REMOTE TERMINAL EQUIPMENT
Transmit DS3
Framer
Receive DS3
Framer
Near-End Terminal
Remote
Terminal
Equipment
Remote
Terminal
Equipment
Transmit DS3
Framer
Receive DS3
Framer
Near-End Terminal
Remote
Terminal
Equipment
Remote
Terminal
Equipment
FEBE bits
11
1
Outbound DS3 Frame