XR72L52 Datasheet, PDF (432/480 Pages) Exar Corporation – TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L52
REV. 1.0.1
xr
TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
FIGURE 185. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, TRANSMITTING AN E3 FRAME (TO THE
REMOTE TERMINAL) WITH THE FEBE BIT (WITHIN THE MA BYTE-FIELD) SET TO “0”
Local Terminal
FEBE bit
x0xxxxxx
Transmit E3
Framer
Receive E3
Framer
MA Byte
Remote
Terminal
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 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 Re-
ceive 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.
416