
Data Sheet
77
Rev. 1.0, 2005-06-02
OctalLIU
TM
PEF 22508 E
Functional Description
3.9.7
Transmit Line Monitor
The transmit line monitor (see principle in Figure 34) compares the transmit line current on XL1 and XL2 with an
on-chip transmit line current limiter. The monitor detects faults on the primary side of the transformer indicated by
a highly increased transmit line current (more than 120 mA for at least 3 consecutive pulses sourced by VDDX)
and protects the device from damage by setting the transmit line driver XL1/2 into high-impedance state
automatically (if enabled by XPM2.DAXLT = 0, see XPM2). The current limiter checks the actual current value
of XL1/2 and if the transmit line current drops below the detection limit the high-impedance state is cleared.
Two conditions are detected by the monitor:
Transmit line ones density (more than 31 consecutive zeros) indicated by LSR1.XLO (LSR1).
Transmit line high current indicated by LSR1.XLS.
In both cases a transmit line monitor status change interrupt is provided.
Shorts between XL1 or XL2 and V
DD, VDDC or VDDP are not detected.
Note that shorts between XL1 and XL2 were not detected. This way a short between XL1 and XL2 will not ham
the device.
Figure 34
Transmit Line Monitor Configuration
Table 27
Recommended Pulse Shaper Programming for E1 with registers TXP(16:1)
R
SER
Z
0
Transmit
Line
Interface
Mode
TXP values, decimal
(
)
(
)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
2
1)
1) The values in this row refers to an ideal application without any parasitics. Any other parasitic resistances have to be taken
into account when calculating the final value of the output serial resistors.
120
Generic
42
40
42
0
7.5
120
Non generic 63
57
-4
0
2
75
Generic
42
40
0
7.5
75
Non generic 60
58
0
--
Reset values
56
0
2
DCIM
Mode
Generic
20
-20 -20 -20 -20 -20 -20 -20 -20
7.5
DCIM
mode
Non generic 28
28
-28 -28 -28 -28 -28 -28 -28 -28
ITS10936
Pulse
Shaper
Monitor
Line
TRI
XDATA
XL1
XL2