XRT73LC00A Datasheet, PDF (45/53 Pages) Exar Corporation – E3/DS3/STS-1 LINE INTERFACE UNIT

xr
PRELIMINARY
XRT73LC00A
E3/DS3/STS-1 LINE INTERFACE UNIT
REV. P1.0.0
The Transmit Drive Monitor feature performs monitor-
ing of the line in the Transmit Direction for the occur-
rence of fault conditions such as a short circuit on the
line or a defective Transmit Drive in the
XRT73LC00A.
The Transmit Drive Monitor is activated by connecting
the MTIP pin (pin 44) to the TTIP line through a 270 Ω
resistor connected in series and by connecting the
MRING pin (pin 43) to the TRING line through a 270
Ω resistor connected in series, as illustrated in
Figure 32.
FIGURE 32. THE XRT73LC00A EMPLOYING THE TRANSMIT DRIVE MONITOR FEATURES
TTIP
TRING
T1
R1 = 31.6 Ω
R2 = 31.6 Ω
1:1
R5 = 75Ω
MTIP
R3 = 270 Ω
MRING
R4 = 270 Ω
When the Transmit Drive Monitor circuitry is connect-
ed to the line as illustrated in Figure 26, then it moni-
tors the line for transitions. As long as the Transmit
Drive Monitor circuitry detects transitions on the line
via the MTIP and MRING pins, it keeps the DMO
(Drive Monitor Output) signal “Low”. However, if the
Transmit Drive Monitor circuit detects no transitions
on the line for 128±32 TCLK periods, then the DMO
signal toggles “High”.
NOTES:
1. The Transmit Drive Monitor circuit does not have to
be used to operate the Transmit Section of the
XRT73LC00A. This is purely a diagnostic feature.
2. The Transmit Drive Monitor feature can also be
used to monitor the Transmit Output Line Signal of
another LIU IC as illustrated in Figure 33.
42