XRT74L73 Datasheet, PDF (449/488 Pages) Exar Corporation – 3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

PRELIMINARY
XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
However, if the locally computed BIP-8 value does
not match the EM byte of the corresponding E3
frame, then the Receive E3 Framer block will do the
following.
• It will inform the Remote Terminal of this fact by
having the Local Transmit E3 Framer block send
the Remote Terminal an E3 frame, with the FEBE
bit-field, within the MA byte, set to “1”. This phe-
nomenon is illustrated below in Figure 205 and
Figure 206 .
Figure 205 illustrates the Local Receive E3 Framer
receiving an errored E3 frame. In this figure, the Lo-
cal Receive E3 Frame block is receiving an E3 frame
with an EM byte containing the value “0x5A”. This
value does not match the locally computed EM byte
value of “0x5B”. Consequently, there is an error in
this E3 frame.
Figure 206 illustrates the subsequent action of the
Local Transmit E3 Framer block, which will transmit
an E3 frame, with the FEBE bit-field set to “1” to the
Remote Terminal. This signaling indicates that the
Local Receive E3 Framer block has received an er-
rored E3 frame.
FIGURE 205. THE LOCAL RECEIVE E3 FRAMER BLOCK, RECEIVING AN E3 FRAME FROM THE REMOTE TERMINAL
WITH AN INCORRECT EM BYTE.
Local Terminal
Transmit E3
Framer
Receive E3
Framer
EM Byte
0x5A
0x5B
Locally Calculated
EM Byte
Remote
Terminal
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