Preliminary Information
MT9076
1.0 MT9076 Line Interface Unit (LIU)
1.1
Receiver
The receiver portion of the MT9076 LIU consists of an input signal peak detector, an optional equalizer with
separate high pass sections, a smoothing filter, data and clock slicers and a clock extractor. Receive
equalization gain can be set manually (i.e., software) or it can be determined automatically by peak detectors.
The output of the receive equalizer is conditioned by a smoothing filter and is passed on to the clock and data
slicer. The clock slicer output signal drives a phase locked loop, which generates an extracted clock (Exclk).
This extracted clock is used to sample the output of the data comparator.
In T1 mode, the receiver portion of the LIU can recover clock and data from the line signal for loop lengths of 0
- 6000 ft. and tolerate jitter to the maximum specified by AT&T TR 62411(Figure 3).
The LOS output pin function is selectable to indicate any combination of loss of signal and/or loss of basic
frame synchronization condition.
The LLOS (Loss of Signal) status bit indicates when the receive signal level is lower than the analog threshold
for at least 1 millisecond, or when the number of consecutive received zeros exceeds the digital loss threshold.
In E1 mode, the analog threshold is either of -20 dB or -40 dB. The digital loss threshold is either 32 or 192.
In T1 mode, the receive LIU circuit requires a terminating resistor of 17.4Ω across the device side of the
receive 2.4:1 transformer.
In E1 mode, the receive LIU circuit requires a terminating resistor of either 20.8Ω or 13Ω across the device side
of the receive 2.4:1 transformer.
The jitter tolerance of the clock extractor circuit exceeds the requirements of TR 62411 in T1 mode (see Figure
3) and G.823 in E1 mode (see Figure 4).
Peak to Peak
Jitter Amplitude
(log scale)
138UI
100UI
28UI
10UI
1.0UI
0.4UI
Jitter Frequency
(log scale)
0.1Hz 1.0Hz
10Hz
4.9Hz
100Hz
1.0kHz 10kHz 100kHz
Figure 3 - Input Jitter Tolerance as Recommended by TR-62411 (T1)
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MITEL [ MITEL NETWORKS CORPORATION ]
