lxt6155 Intel Corporation, lxt6155 Datasheet - Page 21

• Manufacturer Part Number: lxt6155
• Description: 155 Mbps Sdh/sonet/atm Transceiver
• Manufacturer: Intel Corporation

2.5.1.2
2.5.1.3
2.5.1.4
2.5.1.5
Datasheet
Loopback Test (RLIS and LLIS pins)
The LXT6155 allows two types of loopback test: Remote loopback and Local loopback. In Remote
loopback, the received data and clock are looped back to the transmit line interface. The LXT6155
still outputs recovered data and clock at the system interface. In Local loopback, the transmit data
is looped back to the receive input at the line interface. The LXT6155 also transmit data onto the
line interface while looping back. For descriptive diagrams, please refer to Figures 13 and 14.
Line Interface Selection (MODE Pin)
The MODE pin sets one of the two line interfaces, as described in Table 5.
Parallel/Serial Mode Selection (SP pin)
In Hardware Mode, HWSEL = Low, the LXT6155 can be set to operate in serial or parallel data
mode, depending on how the Serial/Parallel SP pin is set.
Setting the SP pin = High sets the LXT6155 to an 8-bit parallel mode. Parallel pins TPID<7:0>,
TPICLK, RPOD<7:0>, ROFP, RPOCLK, LOCK and LOS are be used. Serial pins TPOS, TNEG,
TSICLKP, TSICLKN, RPOS, RNEG, RSOCLKP, RSOCLKN are unused and should be left open.
Setting the SP pin = Low sets the LXT6155 to serial mode. Pins TPOS, TNEG, TSICLKP,
TSICLKN, RPOS, RNEG, RSOCLKP, RSOCLKN, LOCK and LOS are used. Pins TPID<7:0>,
TPICLK, RPOD<7:0> and RPOCLK are unused and should be left open.
Tx Amplitude Trim
In Hardware, serial, coax mode, the line driver output amplitude can be controlled via pins 16 to
20. Setting TXTRIMENA (pin #20) high enables the trim capability. The trim rage is -21% to
+24% in 3% steps controlled by TXTRIM0-TXTRIM3. The minimum amplitude is at 0000 and the
maximum amplitude is at 1111. This is the same control range as in SW mode.
Table 4.
Table 5.
Loopback Selection
MODE Line Interface Settings
MODE
RLIS
High
High
Low
Low
High
Low
Sets LVPECL NRZ mode to interface to a fiber
optic module. CMI related blocks (e.g. input/output
buffers, equalizer) are disabled.
Sets CMI mode to interface to a transformer and a
75
are disabled.
LLIS
High
High
Low
Low
coax cable. NRZ related input/output buffers
Normal operation. No loopback testing.
Local loopback test activate.
Remote loopback test activate.
155 Mbps SDH/SONET/ATM Transceiver — LXT6155
Description
Description
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