Dallas Semiconductor MAXIM DS21354, Manual

Page: 89 / 124

DS21354/DS21554 3.3V/5V E1 Single-Chip Transceivers
89 of 124
15.5.
Receive Monitor Mode
When connecting to a monitor port, a large resistive loss is incurred due to the voltage divider between
the E1 line termination resistors (Rt) and the monitor port isolation resistors (Rm), as shown in
Figure 15-8 . The receiver of the DS21354/DS21554 can provide gain to overcome the resistive loss of a
monitor connection. This is typically a purely resistive loss/gain and should not be confused with the
cable loss characteristics of an E1 transmission line. Via the TEST3 register as shown in
Table 15-4 , the
receiver can be programmed to provide both 12dB and 30dB of gain.
Figure 15-8. Typical Monitor Port Application
Table 15-4. Receive Monitor Mode Gain
TEST3 (Address = AC hex)
REGISTER VALUE
GAIN (dB)
72 hex 12
70 hex 30
PRIMARY
E1 TERMINATING
DEVICE
MONITOR
PORT JACK
E1 LINE
X
F
M
R
DS21X54
Rt
Rm Rm
SECONDARY E1
TERMINATING
DEVICE