XRT72L50 Datasheet, PDF (190/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
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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) FBit Mask(8)
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 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 XRT72L50 Framer IC is a digital device that takes DS3 payload and overhead bit information from some
terminal equipment, processes this data and ultimately, multiplexes this information into a series of outbound
DS3 frames. However, for DS3 coaxial cable applications, the XRT72L50 Framer IC lacks the current 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 comply with the Isolated Pulse Template requirements and be received by
the remote receiver. Therefore, in order to get around this problem, the Framer IC requires 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 Equipment. Figure 53 presents a circuit drawing depicting the Framer IC interfacing to an LIU
(XRT73L00 DS3/E3/STS-1 Transmit LIU).
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