XRT72L58 Datasheet, PDF (314/486 Pages) Exar Corporation – EIGHT CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L58
EIGHT CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
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PRELIMINARY
FIGURE 122. THE BEHAVIOR OF TXPOS AND TXNEG SIGNALS DURING DATA TRANSMISSION WHILE THE TRANSMIT
DS3 LIU INTERFACE IS OPERATING IN THE UNIPOLAR MODE
Data _{1 0 1 1 0 0 1 0 0 1 1 1 0 1 0 1 0 0 1}
TxPOS
1 10
01
TxNEG
TxLineClk
Frame Boundary
When the Transmit E3 LIU Interface block is operating
in the Bipolar (or Dual Rail) mode, then the contents
of the E3 Frame is output via both the TxPOS and Tx-
NEG pins. If the Bipolar mode is chosen, then E3 da-
ta can be transmitted to the LIU via one of two differ-
ent line codes: Alternate Mark Inversion (AMI) or High
Density Bipolar -3 (HDB3). Each one of these line
codes will be discussed below. Bipolar mode is
sometimes referred to as Dual Rail because the data
pulses occur in two polarities: positive and negative.
The role of the TxPOS, TxNEG and TxLineClk output
pins, for this mode are discussed below.
TxPOS - Transmit Positive Polarity Pulse: The
Transmit E3 LIU Interface block will assert this output
to the LIU IC when it desires for the LIU to generate
and transmit a positive polarity pulse to the remote
terminal equipment.
TxNEG - Transmit Negative Polarity Pulse: The
Transmit E3 LIU Interface block will assert this output
to the LIU IC when it desires for the LIU to generate
and transmit a negative polarity pulse to the remote
terminal equipment.
TxLineClk - Transmit Line Clock: The LIU IC uses
this signal from the Transmit E3 LIU Interface block to
sample the state of its TxPOS and TxNEG inputs.
The results of this sampling dictates the type of pulse
(positive polarity, zero, or negative polarity) that it will
generate and transmit to the remote Receive E3
Framer.
5.2.5.1 Selecting the various Line Codes
The user can select either the Unipolar Mode or Bipo-
lar Mode by writing the appropriate value to Bit 3 of
the I/O Control Register (Address = 0x01), as shown
below.
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC LOC
Disable AMI/ZeroSup* Unipolar/
RxLOC
Bipolar*
TxLine CLK RxLine CLK
Invert
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 57 relates the value of this bit field to the Trans-
mit E3 LIU Interface Output Mode.
TABLE 57: THE RELATIONSHIP BETWEEN THE CONTENT OF BIT 3 (UNIPOLAR/BIPOLAR*) WITHIN THE UNI I/O
CONTROL REGISTER AND THE TRANSMIT E3 FRAMER LINE INTERFACE OUTPUT MODE
BIT 3
0
1
TRANSMIT E3 FRAMER LIU INTERFACE OUTPUT MODE
Bipolar Mode: AMI or HDB3 Line Codes are Transmitted and Received
Unipolar (Single Rail) Mode of transmission and reception of E3 data is selected.
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