
XRT79L71
PRELIMINARY
265
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
nibble value (which resides within the very next incoming E3 frame) is of the value "0xD". As a consequence,
a BIP-4 nibble error is being detected at this time.
In response to this erred condition, the Transmit E3 Framer (within the Near-End Terminal) will respond by
setting the "A" bit, within the very next outbond E3 frame to the value "1" in order to denote a FEBE/REI event.
More specifically, the Transmit E3 Framer (within the Near-End Terminal) will transmit an E3 frame (with the
"A" bit set to "1") each time the corresponding Receive E3 Framer (also within the Near-End Terminal) detects
a BIP-4 nibble error within an E3 frame. Figure 121 presents an illustration of the Transmit E3 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
(within the XRT79L71) handles the "A" bit (when configured to function as the FEBE/REI indicator bit) can be
and
The "N" (National) Bit
The "N" bit is referred to (in the ITU-T G.751 Specification) as the National Bit. In the case of the XRT79L71, it
permits the user to perform any of the following tasks with the "N" bit.
FIGURE 120. A SIMPLE ILLUSTRATION OF A NEAR-END TERMINAL DETECTING BIP-4 NIBBLE ERRORS WITHIN ITS
INCOMING
E3 SIGNAL
FIGURE 121. A SIMPLE ILLUSTRATION OF THE NEAR-END TERMINAL EQUIPMENT TRANSMITTING THE FEBE/REI
INDICATOR TO THE REMOTE TERMINAL EQUIPMENT
Transmit E3
Framer
Receive E3
Framer
Near-End Terminal
Remote
Terminal
Equipment
Remote
Terminal
Equipment
BIP-4 Nibble
Locally Calculated
EM Byte
0xD
0xC
Transmit E3
Framer
Receive E3
Framer
Near-End Terminal
Remote
Terminal
Equipment
Remote
Terminal
Equipment
1
A Bit