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XRT7250 Datasheet, PDF (406/463 Pages) Exar Corporation – DS3/E3 FRAMER IC
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XRT7250
DS3/E3 FRAMER IC
REV. 1.1.1
FIGURE 188. ILLUSTRATION ON HOW THE RECEIVE E3 FRAMER (WITHIN THE XRT7250 FRAMER IC) BEING INTER-
FACE TO THEXRT7300 LINE INTERFACE UNIT, WHILE THE FRAMER IS OPERATING IN BIPOLAR MODE
TxSER
TxInClk
TxFrame
NIBBLEINTF
RESETB
INTB
CSB
RW
DS
AS
INTB
A[8:0]
D[7:0]
5V
RxSer
RxClk
RxFrame
RxLOS
RxOOF
RxRED
RxAIS
U1
46
43
61
TxSER
TxInClk
TxFrame
25 NIBBLEINTF
28
RESETB
13
8
7
10
9
6
INTB
CSB
WRB_RW
RDB_DS
ALE_AS
Rdy_Dtck
15
16 A0
17 A1
18
19
20
21
22
23
A2
A3
A4
A5
A6
A7
A8
32
33 D0
34
35
36
37
38
39
D1
D2
D3
D4
D5
D6
D7
27
MOTO
86
88
90
RxSer
RxClk
RxFrame
95
94
RxLOS
93 RxOOF
87 RxRED
RxAIS
XRT7250
TxPOS 65
TxNEG 64
63
TxLineClk
DMO 79
ExtLOS 78
RLOL 77
69
LLOOP
RLOOP 70
TAOS 68
TxLEV 67
66
ENCODIS
REQB 71
76
RxPOS
RxNEG 75
RxLineClk 74
U2
37 TPDATA
38 TNDATA
36
TCLK
4 DMO
24 RLOS
23 RLOL
14
LLB
15 RLB
2 TAOS
1 TxLEV
21
ENCODIS
12 REQDIS
33
RPOS
32 RNEG
31 RCLK1
XRT7300
TTIP 41
40
TRING
MTIP 44
43
MRING
1 R3 2
270
1 R4 2
270
R1
1
2
36
1 T1 5
R2
1
2
36
4
8
1:1
TTIP
TRING
8
RTIP
RRING 9
C1
12
0.01uF
R5
37.5
R6
37.5
1 T2 5
4
8
1:1
RTIP
RRING
6.3.1.2.1 AMI Decoding
AMI or Alternate Mark Inversion, means that consec-
utive "one's" pulses (or marks) will be of opposite po-
larity with respect to each other. This line code in-
volves the use of three different amplitude levels: +1,
0, and -1. The +1 and -1 amplitude signals are used
to represent one's (or mark) pulses and the "0" ampli-
tude pulses (or the absence of a pulse) are used to
represent zeros (or space) pulses. The general rule
for AMI is: if a given mark pulse is of positive polarity,
then the very next mark pulse will be of negative po-
larity and vice versa. This alternating-polarity rela-
tionship exists between two consecutive mark pulses,
independent of the number of zeros that exist be-
tween these two pulses. Figure 189 presents an illus-
tration of the AMI Line Code as would appear at the
RxPOS and RxNEG pins of the Framer, as well as the
output signal on the line.
387
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