XRT74L73 Datasheet, PDF (234/488 Pages) Exar Corporation – 3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
PRELIMINARY
The user can configure the Receive DS3 LIU Inter-
polar Mode by writing the appropriate data to the I/O
face block to operate in either the Unipolar or the Bi- Control Register, as depicted below.
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
Disable
TxLOC
R/W
BIT 6
LOC
RO
BIT 5
Disable
RxLOC
R/W
BIT 4
AMI/ZeroSup*
R/W
BIT 3
Unipolar/
Bipolar*
R/W
BIT2
BIT 1
TxLine CLK RxLine CLK
Invert
Invert
R/W
R/W
BIT 0
Reframe
R/W
1
0
1
0
0
0
0
0
Table 51 relates the value of this bit-field to the Re-
ceive DS3 LIU Interface Input Mode.
TABLE 51: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 3 (UNIPOLAR/BIPOLAR) WITHIN THE I/O CONTROL
REGISTER AND THE TXLINECLK CLOCK EDGE THAT TXPOS AND TXNEG ARE UPDATED ON
BIT 3
0
1
RECEIVE DS3 LIU INTERFACE INPUT MODE
.Bipolar Mode (Dual Rail): AMI or B3ZS Line Codes are Transmitted and Received.
Unipolar Mode (Single Rail) Mode of transmission and reception of DS3 data is selected.
NOTES:
1. The default condition is the Bipolar Mode.
2. This selection also effects the Transmit DS3
Framer Line Interface Output Mode
4.3.1.2 Bipolar Decoding
If the Receive DS3 LIU Interface block is operating in
the Bipolar Mode, then it will receive the DS3 data
pulses via both the RxPOS, RxNEG, and the RxLi-
neClk input pins. Figure 82 presents a circuit dia-
gram illustrating how the Receive DS3 LIU Interface
block interfaces to the Line Interface Unit while the
Framer is operating in Bipolar mode. The Receive
DS3 LIU Interface block can be configured to decode
the incoming data from either the AMI or B3ZS line
codes.
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