XRT72L56 Datasheet, PDF (336/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L56
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
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PRELIMINARY
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
Not Used
R/W
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
BIT 0
RxFERF
RO
1
5.3.2.10 Error Checking of the Incoming E3
Frames
The Receive E3 Framer block can be configured to
performs error-checking on the incoming E3 frame
data that it receives from the Remote Terminal Equip-
ment. If configured accordingly, the Receive E3
Framer block will performs this error-checking by
computing the BIP-4 value of an incoming E3 frame.
Once the Receive E3 Framer block has obtained this
value, it will compare this value with that of the BIP-4
value that it receives, within the very next E3 frame. If
the locally computed BIP-4 value matches the EM
byte of the corresponding E3 frame, then the Receive
E3 Framer block will conclude that this particular
frame has been properly received. The Receive E3
Framer block will then inform the Remote Terminal
Equipment of this fact by having the Local Terminal
Equipment Transmit E3 Framer block send the Re-
mote Terminal an E3 frame, with the “A” bit-field, set
to “0”.
This procedure is illustrated in Figure 138 and
Figure 139, below.
Figure 138 illustrates the Local Receive E3 Framer
receiving an error-free E3 frame. In this figure, the lo-
cally computed BIP-4 value of “0xA” matches that re-
ceived from the Remote Terminal, within the EM byte-
field. Figure 139 illustrates the subsequent action of
the Local Transmit E3 Framer block, which will trans-
mit an E3 frame, with the A bit-field set to “0”, to the
Remote Terminal. This signaling indicates that the
Local Receive E3 Framer has received an error-free
E3 frame.
FIGURE 138. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, RECEIVING AN E3 FRAME (FROM THE
REMOTE TERMINAL) WITH A CORRECT BIP-4 VALUE.
Local Terminal
Transmit E3
Framer
Receive E3
Framer
Locally Calculated
0xA
BIP-4 Nibble
BIP-4 Nibble
Remote
Terminal
0xA
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