XRT72L54 Datasheet, PDF (437/484 Pages) Exar Corporation – FOUR CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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PRELIMINARY
XRT72L54
FOUR CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
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 follow-
ing.
• 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 phenome-
non is illustrated below in Figure 198 and
Figure 199.
Figure 198 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 199 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 198. ILLUSTRATION OF 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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