XRT7300IV View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT7300IV' PDF : 55 Pages View PDF
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FIGURE 28. THE ANALOG LOCAL LOOP-BACK IN THE XRT7300
RLOL EXCLK
XRT7300
E3/DS3/STS-1 LINE INTERFACE UNIT
REV. 1.1.1
RTIP
RRING
REQDIS
LOSTHR
SDI
SDO/LCV
SCLK
CS
REGRESET
TTIP
TRING
TXLEV
TXOFF
DMO
AGC/
Equalizer
Slicer
Clock
Recovery
Peak
Detector
LOS Detector
Data
Recovery
Serial
Processor
Interface
Analog Local
Loop-Back Path
Loop MUX
Invert
HDB3/
B3ZS
Decoder
Pulse
Shaping
HDB3/
B3ZS
Encoder
Device
Monitor
Transmit
Logic
Duty Cycle Adjust
RCLK1
RCLK2
RPOS
RNEG
DECODIS
RLOS
LLB
RLB
ENCODIS
TAOS
TPDATA
TNDATA
TCLK
MTIP
MRING
If the XRT7300 is operating in the HOST Mode:
Access the Microprocessor Serial Interface and write
a “1” into the LLB bit-field and a “0” into the RLB bit-
field in Command Register 4.
COMMAND REGISTER CR4 (ADDRESS = 0X04)
D4
D3
D2
D1
D0
X STS-1/DS3
E3
LLB
RLB
X
X
X
1
0
If the XRT7300 is operating in the Hardware
Mode:
The LLB input pin (pin 14) must be set to “High” and
the RLB input pin (pin 15) must be set to “Low”.
NOTES:
1. The Analog Local Loop-Back Mode does not work
if the transmitter is turned off via the TXOFF fea-
ture.
2. The XRT7300 automatically Declares an LOS Con-
dition anytime it has been configured to operate in
either the Analog Local Loop-Back or Digital Local
Loop-Back Modes. Consequently, the MUTing -
upon -LOS must be disabled prior to configuring
the device to operate in either of these local Loop-
Back modes.
4.2 THE DIGITAL LOCAL LOOP-BACK MODE
When the XRT7300 is configured to operate in the
Digital Local Loop-Back Mode, it ignores any signals
that are input to the RTIP and RRING input pins. The
Transmitting Terminal Equipment transmits clock and
data into the XRT7300 via the TPDATA, TNDATA and
TCLK input pins. This data is processed through the
Transmit Clock Duty Cycle Adjust PLL and the HDB3/
B3ZS Encoder block and then looped back to the
HDB3/B3ZS Decoder block.
Figure 29 illustrates the path that the data takes when
the chip is configured to operate in the Digital Local
Loop-Back Mode.
37
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