XR72L52 Datasheet, PDF (324/480 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 127. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, TRANSMITTING AN E3 FRAME (TO THE
REMOTE TERMINAL) WITH THE A BIT SET TO “0”
Local Terminal
Transmit E3
Framer
Receive E3
Framer
Value = 0
ABit
Remote
Terminal
However, if the locally computed BIP-4 value does not match the BIP-4 value 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 A bit-field set to “1”. This phenomenon is illustrated below in Figure 128 and
Figure 129.
Figure 128 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 BIP-4 containing the value, 0xA. This value does not
match the locally computed BIP-4 value of, 0xB. Consequently, there is an error in the previous E3 frame.
Figure 129 illustrates the subsequent action of the Local Transmit E3 Framer block, which will transmit an E3
frame, with the A 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.
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