XRT72L53 Datasheet, PDF (420/467 Pages) Exar Corporation – THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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PRELIMINARY
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.8
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 phe-
nomenon 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 Local
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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