XRT7250 Datasheet, PDF (304/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

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XRT7250
DS3/E3 FRAMER IC
REV. 1.1.1
FIGURE 129. BEHAVIOR OF THE RXPOS, RXNEG AND RXLINECLK SIGNALS DURING DATA RECEPTION OF UNIPO-
LAR DATA
Data _{1 0 1 1 0 0 1 0 0 1 1 1 0 1 0 1 0 0 1}
RxPOS
1 10
01
RxNEG
RxLineClk
The user can configure the Receive E3 LIU Interface Mode by writing the appropriate data to the I/O Con-
block to operate in either the Unipolar or the Bipolar trol Register, as depicted below.
II/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC LOC
Disable AMI/ZeroSup* Unipolar/
RxLOC
Bipolar*
TxLine CLK RxLine CLK
Invert
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 59 relates the value of this bit-field to the Re-
ceive E3 LIU Interface Input Mode.
TABLE 59: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TXLINECLK INV) WITHIN THE I/O CONTROL
REGISTER AND THE TXLINECLK CLOCK EDGE THAT TXPOS AND TXNEG ARE UPDATED ON
BIT 3
0
1
RECEIVE E3 LIU INTERFACE INPUT MODE
.Bipolar Mode (Dual Rail): AMI or HDB3 Line Codes are Transmitted and Received.
Unipolar Mode (Single Rail) Mode of transmission and reception of E3 data is selected.
NOTES:
1. The default condition is the Bipolar Mode.
2. This selection also effects the Transmit E3 Framer
Line Interface Output Mode
5.3.1.2 Bipolar Decoding
If the Receive E3 LIU Interface block is operating in
the Bipolar Mode, then it will receive the E3 data puls-
es via both the RxPOS, RxNEG, and the RxLineClk
input pins. Figure 130 presents a circuit diagram il-
lustrating how the Receive E3 LIU Interface block in-
terfaces to the Line Interface Unit while the Framer is
operating in Bipolar mode. The Receive E3 LIU Inter-
face block can be configured to decode either the AMI
or HDB3 line codes.
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