XRT72L50 Datasheet, PDF (304/471 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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FIGURE 117. 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 block to operate in either the Unipolar or the Bipolar Mode
by writing the appropriate data to the I/O Control Register, as depicted below.
I/O Control Register (Address = 0x01)
BIT 7
Disable TxLOC
BIT 6
LOC
R/W
RO
1
0
BIT 5
Disable
RxLOC
R/W
1
BIT 4
AMI/ZeroSup*
R/W
0
BIT 3
Unipolar/
Bipolar*
R/W
0
BIT2
BIT 1
TxLine CLK RxLine CLK
Invert
Invert
R/W
R/W
0
0
BIT 0
Reframe
R/W
0
Table 56 relates the value of this bit-field to the Receive E3 LIU Interface Input Mode.
TABLE 56: 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 pulses via
both the RxPOS, RxNEG, and the RxLineClk input pins. Figure 118 presents a circuit diagram illustrating how
the Receive E3 LIU Interface block interfaces to the Line Interface Unit while the Framer is operating in Bipolar
mode. The Receive E3 LIU Interface block can be configured to decode either the AMI or HDB3 line codes.
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