XRT72L50 Datasheet, PDF (425/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
• 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 phenomenon is illustrated
below in Figure 186 and Figure 187.
Figure 186 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 187 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 errored E3 frame.
FIGURE 186. 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
412