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XRT79L71
PRELIMINARY
65
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
In response to this erred condition, the Transmit DS3 Framer within the Near-End Terminal will respond by
setting the three (3) FEBE bits, within each of its outbound DS3 frames to some value other than [1, 1, 1] in
order to denote a FEBE (Far-End Block Error) or REI (Remote Error Indicator) event. More specifically, the
Transmit DS3 Framer within the Near-End Termina) will transmit this FEBE/REI indicator (e.g., a DS3 frame
with the FEBE bit-fields set to some value other than [1, 1, 1]) each time the corresponding Receive DS3
Framer, also within the Near-End Terminal, detects either a CP-bit or Framing bit error within a DS3 frame.
Figure 23 presents an illustration of the Transmit DS3 Framer sending the FEBE/REI indicator to the Remote
Terminal Equipment.
A more detailed discussion on how the Transmit DS3/E3 Framer block and the Receive DS3/E3 Framer block,
The FERF/RDI (Far-End Receive Failure/Remote Defect Indicator) - X-Bits
The purpose of the X-bits within the DS3 frame is to permit a given DS3 Terminal Equipment to transmit the
FERF/RDI indicator to the remote terminal equipment.
Whenever a Near-End DS3 Terminal declares a
service-affecting defect condition (e.g., the LOS, LOF/OOF or the AIS defect condition) within its incoming DS3
data-stream, then it will inform the remote terminal equipment (e.g., the source of this defective DS3 signal) of
this fact by transmitting the FERF/RDI indicator back out to the Remote Terminal Equipment via the outbound
(returning) DS3 signal. This Near-End DS3 Terminal will indicate the FERF/RDI condition by setting both of the
X-bits, within each outbound DS3 frame to "0", for the duration that the Receive-related/Service-affecting
FIGURE 22. A SIMPLE ILLUSTRATION OF A NEAR-END TERMINAL DETECTING FRAMING BIT ERRORS WITHIN ITS
INCOMING
DS3 SIGNAL
FIGURE 23. A SIMPLE ILLUSTRATION OF THE NEAR-END TERMINAL EQUIPMENT TRANSMITTING THE FEBE/REI INDI-
CATOR TO THE REMOTE TERMINAL EQUIPMENT
Transmit DS3
Framer
Receive DS3
Framer
Near-End Terminal
Remote
Terminal
Equipment
Remote
Terminal
Equipment
Detecting F-bit Errors
Erred DS3 Data-stream
Transmit DS3
Framer
Receive DS3
Framer
Near-End Terminal
Remote
Terminal
Equipment
Remote
Terminal
Equipment
FEBE bits
01
1
Outbound DS3 Frame
Detecting F-bit Errors