XRT75L03 Datasheet, PDF (88/92 Pages) Exar Corporation – THREE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR

XRT75L03
REV. 1.0.4
THREE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR
8.2.1 ANALOG LOOPBACK:
In this mode, the transmitter outputs (TTIP_n and TRING_n) are connected internally to the receiver inputs
(RTIP_n and RRING_n) as shown in Figure 26. Data and clock are output at RCLK_n, RPOS_n and RNEG_n
pins for the corresponding transceiver. Analog loopback exercises most of the functional blocks of the device
including the jitter attenuator which can be selected in either the transmit or receive path.
XRT75L03 can be configured in Analog Loopback either in Hardware mode via the LLB_n and RLB_n pins or
in Host mode via LLB_n and RLB_n bits in the channel control registers.
NOTES:
1. In the Analog loopback mode, data is also output via TTIP_n and TRING_n pins.
2. Signals on the RTIP_n and RRING_n pins are ignored during analog loopback.
FIGURE 26. ANALOG LOOPBACK
TCLK
TPDATA
TNDATA
1
HDB3/B3ZS
ENCODER
TIMING
CONTROL
Tx
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
85