Datasheet

DS26518 8-Port T1/E1/J1 Transceiver
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9.12.3.4 Receiver Monitor Mode
The receive equalizer is equipped with a monitor mode function that is used to overcome the signal attenuation
caused by the resistive bridge used in monitoring applications. This function allows for a resistive gain of up to
32dB along with cable attenuation of 12dB to 30dB as shown in the LIU Receive Control Register (
LRCR).
Figure 9-25. Typical Monitor Application
PRIMARY
T1/E1 TERMINATING
DEVICE
MONITOR
PORT JACK
T1/E1 LINE
X
F
M
R
DS2651x
Rt
Rm Rm
SECONDARY T1/E1
TERMINATING
DEVICE
9.12.3.5 Loss of Signal
The DS26518 uses both the digital and analog loss-detection method in compliance with the latest T1.231 for
T1/J1 and ITU-T G.775 or ETS 300 233 for E1 mode of operation.
LOS is detected if the receiver level falls bellow a threshold analog voltage for certain duration. Alternatively, this
can be termed as having received “zeros” for a certain duration. The signal level and timing duration are defined in
accordance with the T1.231 or G.775 or ETS 300 233 specifications.
For short-haul mode, the loss-detection thresholds are based on cable loss of 12dB to 18dB for both T1/J1 and E1
modes. The loss thresholds are selectable based on
Table 10-22. For long-haul mode, the LOS-detection threshold
is based on cable loss of 30dB to 38dB for T1/J1 and 30dB to 45dB for E1 mode. Note there is no explicit bit called
short-haul mode selection. Loss declaration level is set at 3dB lower than the maximum sensitivity setting
programmed in
Table 10-22.
The loss state is exited when the receiver detects a certain ones density at the maximum sensitivity level or higher,
which is 3dB higher than the loss-detection level. The loss-detection signal level and loss-reset signal level are
defined with hysteresis to prevent the receiver from bouncing between “LOS” and “no LOS” states.
Table 9-43
outlines the specifications governing the loss function.