XRT75L02 Datasheet, PDF (45/50 Pages) Exar Corporation – TWO CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER

XRT75L02
TWO CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER
FIGURE 26. ANALOG LOOPBACK
TCLK
TPDATA
TNDATA
1
HDB3/B3ZS
ENCODER
TIMING
CONTROL
Tx
xr
REV. 1.0.3
TTIP
TRING
RCLK
RPOS
RNEG
1
HDB3/B3ZS
DECODER
DATA &
CLOCK
Rx
RECOVERY
1 _{if enabled}
2 _{if enabled and selected in either Receive or Transmit path}
RTIP
RRING
8.2.2 DIGITAL LOOPBACK:
The Digital Loopback function is available either in Hardware mode or Host mode. When the Digital Loopback
is selected, the transmit clock (TxClk_n) and transmit data inputs (TPOS_n & TNEG_n) are looped back and
output onto the RxClk_n, RPOS_n and RNEG_n pins as shown in Figure 27. The data presented on TxClk,
TPOS and TNEG are not output on the TTIP and TRING pins.This provides the capability to configure the
protection card (in redundancy applications) in Digital Loopback mode without affecting the traffic on the
primary card.
NOTE: Signals on the RTIP_n and RRING_n pins are ignored during digital loop back.
FIGURE 27. DIGITAL LOOPBACK
TCLK
TPDATA
TNDATA
1
HDB3/B3ZS
ENCODER
TIMING
Tx
CONTROL
TTIP
TRING
RCLK
RPOS
RNEG
1
HDB3/B3ZS
DECODER
DATA &
CLOCK
Rx
RECOVERY
1 _{if enabled}
2 _{if enabled and selected in either Receive or Transmit path}
RTIP
RRING
8.2.3 IREMOTE LOOPBACK:
With Remote loop back activated as shown in Figure 28, the receive data on RTIP and RRING is looped back
after the jitter attenuator (if selected in receive or transmit path) to the transmit path using RxClk as transmit
timing. The receive data is also output via the RPOS and RNEG pins.
During the remote loop back mode, if the jitter attenuator is selected in the transmit path, the receive data after
the Clock and Data Recovery Block is looped back to the transmit path and passed through the jitter attenuator
using RxClk as the transmit timing.
NOTE: Input signals on TxClk, TPOS and TNEG are ignored during Remote loop back.
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