lxt6155 Intel Corporation, lxt6155 Datasheet - Page 16

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

16
LXT6155 — 155 Mbps SDH/SONET/ATM Transceiver
2.2.2.1
2.2.2.2
2.2.2.3
Figure 3. Framing State
Figure 4. Criteria for LOS Output
frames with incorrect frame words are required. Byte alignment occurs when entering the in-frame
state. In case of an OOF event, the byte alignment and frame pulse position are frozen. The ROFP
output continues unchanged until re-entering the in-frame state.
Loss of Signal (LOS)
Loss of Signal provides an alarm signal indicating incoming signal voltage is weak or incoming
data does not contain enough transitions. This signal is available in HW mode on pin #45 and in
SW mode as status and interrupt (Reg #15, modes 00 and 05).
Coax Interface
Loss of Signal provides an alarm output that indicates weak line input signal. The LOS signal
asserts when the incoming signals fall below a specified loss threshold, and de-asserts when the
line signal rises nominally 2dB above the assert threshold. The threshold is adjustable in SW mode
(HWSEL = High) via the Processor interface.
Fiber Interface
If no transition is detected during any 3112 bit times (20 sec), LOS asserts. LOS is cleared when
two consecutive frame words with no LOS events between then are received. In SW mode
(HWSEL = High) the assertion window is programmable from 128 bits to 4096 bits in four steps.
The deassertion criteria can also be configured to 12.5% transition density. The 12.5% density is
determined by receipt of at least 4 transitions during a 32 bit sliding window.
In Frame
De-assert
Assert
LOS
LOS
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4 consecutive frames
2 consecutive frames
Nominal Value
with errored FAS
with correct FAS
HYS = 3 dB
Level below nominal
Out of Frame
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