lxt6155 Intel Corporation, lxt6155 Datasheet - Page 14

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

14
LXT6155 — 155 Mbps SDH/SONET/ATM Transceiver
2.1.2.1
2.1.3
2.2
2.2.1
2.2.1.1
Figure 2. LXT6155 System Interface
or Coax Transformers
Fiber Optic Modules
Line Interface
CMI Encoding
Coded Mark Inversion (CMI) is an encoding scheme adopted by SONET STS-3 and SDH STM1
standards. CMI encoding guarantees at least one transition per bit, thereby enhancing the clock
recovery process. CMI encodes a “0” with a midpoint positive transition, and a “1” as Low or
High, in opposite polarity to the previous encoded “1”. Refer to Figures 6, 24 and 25 for encoding
and pulse template information.
Tx Clock Monitoring
The LXT6155 provides transmit clock monitoring for both serial and parallel operating modes.
When using the crystal clock as a reference, the LXT6155 monitors the TSICLKP/TSICLKN or the
TPICLK input(s) for transitions. If no transition is seen within 200ns, the tx_clk_alarm flag will be
set (reg #15) and the transmitter outputs ttip1/tring1 or ttip0/tring0 will stop sending data to the line.
This condition will remain until the LXT6155 detects clock transitions at the transmitter input(s)
TSICLKP/TSICLKN or TPICLK. Transmit clock monitoring can be disabled in software mode
only.
In remote loopback, transmit clock monitoring is disabled in SW and HW mode. In SW mode, when
using transmit clocks as the receive PLL reference, the user must disable transmit clock monitoring
by setting reg #1 bit <0> low.
Receiver
Analog Front End and Timing Recovery
CMI Mode
Received data on RTIP/RRING goes through an adaptive equalizer. An adaptive
adaptive Automatic Gain Control (AGC) compensate the frequency-and-cable length dependent
loss in data signal, and reshapes the signal to the optimal waveform. A Phase Locked Loop (PLL)
2
2
LXT6155
(optional)
Processor
Rx
Tx
4
1
2
1
2
Data/Clock (8-bit parallel or serial mode)
Data/Clock (8-bit parallel or serial mode)
Receive Output Frame Pulse (ROFP)
Receive Ouput PLL Lock (LOCK)
Loss of Signal (LOS)
System Interface
SONET/SDH
Terminator
Overhead
ATM UNI
f
equalizer and
Datasheet