xrt75r12 Exar Corporation, xrt75r12 Datasheet - Page 39

• Manufacturer Part Number: xrt75r12
• Description: Twelve Channel E3/ds3/sts-1 Line Interface Unit With Jitter
• Manufacturer: Exar Corporation

REV. 1.0.4
This feature is used for monitoring the transmit line for occurrence of fault conditions such as a short circuit on
the line or a defective line driver. To activate this function, connect MTIP_n pins to the TTIP_n lines via a 270
resistor and MRing_n pins to TRing_n lines via 270 resistor as shown in
When the MTIP_n and MRing_n are connected to the TTIP_n and TRing_n lines, the drive monitor circuit
monitors the line for transitions. The DMO_n (Drive Monitor Output) will be asserted “Low” as long as the
transitions on the line are detected via MTIP_n and MRing_n. If no transitions on the line are detected for 128
± 32 TxClk_n periods, the DMO_n output toggles “High” and when the transitions are detected again, DMO_n
toggles “Low”.
N
The transmitter section of each channel can either be turned on or off. To turn on the transmitter, set the input
pin TxON to “High” and write a “1” to the TxON_n control bit. When the transmitter is turned off, TTIP_n and
TRing_n are tri-stated.
N
F
4.6
4.7
OTE
OTES
IGURE
1.
2.
: The Drive Monitor Circuit is only for diagnostic purpose and does not have to be used to operate the transmitter.
:
24. T
Transmit Drive Monitor
Transmitter Section On/Off
defective line card and turn on the back-up line card, writing a “1” to the TxON_n control bits transfers the control
to TxON pin.
This feature provides support for Redundancy.
If the XRT75R12 is configured in Host mode, to permit a system designed for redundancy to quickly shut-off the
TxLineClk(n)
TxNEG(n)
TxPOS(n)
RANSMIT
TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR
D
RIVER
M
ONITOR SET
TPData(n)
TNData(n)
TxClk(n)
-
UP
.
MRing(n)
TRing(n)
MTIP(n)
TTIP(n)
36
270
270
R1
R2
31.6 +1%
31.6 + 1%
R1
Figure
R2
24.
1:1
75
R3
XRT75R12