Octal E1 Line Interface — LXT381

Datasheet

15

2.5.1

Analog Loopback

When selected, the transmitter outputs (TTIP & TRING) are connected internally to the receiver

inputs (RTIP & RRING) as shown in Figure 3. Data and clock are output at RCLK, RPOS &

RNEG pins for the corresponding transceiver. Note: Signals on the RTIP & RRING pins are

ignored during analog loopback.

2.5.2

Remote Loopback

During remote loopback, the RCLK, RPOS & RNEG outputs routed to the transmit circuits and

output on the TTIP & TRING pins. Signals on the TCLK, TPOS & TNEG pins are ignored during

remote loopback. See Figure 4. Note: because in a remote loopback, the RPOS/RNEG outputs

determine the transmitter pulse width, the G.703 pulse template may not be met in this test mode.

2.6

Hitless Protection Switching (HPS)

The LXT386 transceivers include an output driver tristatability feature for T1/E1 redundancy

applications. This feature greatly reduces the cost of implementing redundancy protection by

eliminating external relays. Please refer to Application Note 119 for guidelines for implementing

redundancy systems for both T1 and E1 operation using the LXT380/1/4/6.

Figure 3. Analog Loopback

Buffer/

Pulse

Shaper

Data

Recovery

TTIP

TRING

RTIP

RRING

TCLK

TPOS

TNEG

RCLK

RPOS

RNEG

Figure 4. Remote Looback

Buffer/

Pulse

Shaper

Data

Recovery

TTIP

TRING

RTIP

RRING

RCLK

RPOS

RNEG

TCLK

TPOS

TNEG