XRT7250 Datasheet, PDF (192/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

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DS3/E3 FRAMER IC
XRT7250
REV. 1.1.1
TX DS3 F-BIT MASK2 REGISTER, ADDRESS = 0X37
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
FBit Mask(23) FBit Mask(22) FBit Mask(21) FBit Mask(20) FBit Mask(19) FBit Mask(18) FBit Mask(17) FBit Mask(16)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
TX DS3 F-BIT MASK3 REGISTER, ADDRESS = 0X38
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
FBit Mask(15) FBit Mask(14) FBit Mask(13) FBit Mask(12) FBit Mask(11) FBit Mask(10) FBit Mask(9)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
FBit Mask(8)
R/W
0
TX DS3 F-BIT MASK4 REGISTER, ADDRESS = 0X39
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
FBit Mask(7) FBit Mask(6) FBit Mask(5) FBit Mask(4) FBit Mask(3) FBit Mask(2) FBit Mask(1) FBit Mask(0)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
4.2.5 The Transmit DS3 Line Interface Block
The XRT7250 Framer IC is a digital device that takes
DS3 payload and overhead bit information from some
terminal equipment, processes this data and ultimate-
ly, multiplexes this information into a series of out-
bound DS3 frames. However, for DS3 coaxial cable
applications, the XRT7250 Framer IC lacks the cur-
rent drive capability to be able to directly transmit this
DS3 data stream through some transformer-coupled
coax cable with enough signal strength for it to com-
ply with the Isolated Pulse Template requirements
and be received by the remote receiver. Therefore, in
order to get around this problem, the Framer IC re-
quires the use of an LIU (Line Interface Unit) IC. An
LIU is a device that has sufficient drive capability,
along with the necessary pulse-shaping circuitry to
be able to transmit a signal through the transmission
medium in a manner that it can (1) comply with the
DSX-3 Isolated Pulse Template requirements and (2)
be reliably received by the Remote Terminal Equip-
ment. Figure 65 presents a circuit drawing depicting
the Framer IC interfacing to an LIU (XRT7300 DS3/
E3/STS-1 Transmit LIU).
173