peb2255 Infineon Technologies Corporation, peb2255 Datasheet - Page 57

• Manufacturer Part Number: peb2255
• Description: E1/t1/j1 Framer And Line Interface Component For Long And Short Haul Applications
• Manufacturer: Infineon Technologies Corporation

4.1.5
There are different definitions for detecting Loss of Signal (LOS) alarms in the ITU-T
G.775 and ETS 300233. The FALC
is performed by generating an interrupt (if not masked) and activating a status bit.
Additionally a LOS status change interrupt is programmable via register IPC.SCI.
• Detection:
• Recovery:
Note: In long haul mode, LOS alarm is declared either if “no pulses” are detected
Data Sheet
An alarm is generated if the incoming data stream has no pulses (no transitions) for a
certain number (N) of consecutive pulse periods. “No pulse” in the digital receive
interface means a logical zero on pins RDIP/RDIN/ROID. A pulse with an amplitude
less than Q dB below nominal is the criteria for “no pulse” in the analog receive
interface (LIM1.DRS=0). In short haul mode (LIM0.EQON=0) the receive signal level
Q is programmable via three control bits LIM1.RIL2...0 in a range of about 1400 to 200
mV differential voltage between pins RL1/2. In long haul mode (LIM0.EQON=1) the
analog LOS criteria is defined by the equalizer status. The number N can be set via
an 8 bit register PCD. The contents of the PCD register is multiplied by 16, which
results in the number of pulse periods or better, the time which has to suspend until
the alarm has to be detected. The range therefore results from 16 to 4096 pulse
periods. ETS300233 requires detection intervals of at least 1 ms. This time period
results always in a LFA (Loss of Frame Alignment) before a LOS is detected.
In general the recovery procedure starts after detecting a logical “one“ (digital receive
interface) or a pulse (analog receive interface) with an amplitude more than Q dB
(defined by LIM1.RIL2...0, LIM0.EQON=0) of the nominal pulse. The value in the 8 bit
register PCR defines the number of pulses (1 to 255) to clear the LOS alarm.
Additional recovery conditions may be programmed by register LIM2.
for the period defined in PCD or the signal level drops below typically about
-35 dB of the nominal signal (“low signal level”). Additionally, the incoming
data stream is cleared, if this “low signal level” is detected in order to
generate a fixed data stream before first bit errors occur. Typically, this loss
of signal threshold is about -35 dB.
For recovery this means, that at first the signal level has to increase and
then the pulses are counted and compared to PCR to return from LOS
indication.
Please also note, that this behavior is slightly different to FALC-LH V1.1.
Loss of Signal Detection (E1)
®
-LH covers all these standards. The LOS indication
57
Functional Description E1
FALC-LH V1.3
PEB 2255
2000-07