S3045
SONET/SDH OC-12 TO OC-48 MUX/DEMUX
Loss of Signal (LOS)
FRAMER (In-frame, going out-of-frame)
The frame acquisition algorithm determines whether
the receiver is in-frame or out-of-frame. In-frame is
defined as the state where the frame boundaries are
known. Out-of-Frame (OOF) is defined as the state
where the frame boundaries of the incoming signal
are unknown. OOF is also referred to as the Se-
verely Errored Frame (SEF) in the SONET
standards. The frame pulse (FRAME) input of the
S3045 indicates if the frame boundaries are known
(in-frame) or unknown (out-of frame).
The Loss of Signal (LOS) block monitors the incom-
ing data stream for all zero’s. When a minimum of 27
µsec of all zero’s are detected, a loss of signal (LOS)
is declared (high signal). LOS is deactivated (low
signal) when two consecutive valid framing patterns
are detected and no LOS condition is detected in
between. LOS is updated on the falling edge of
POCLKA,B,C,D.
J0 Frame Pulse
The J0 Frame Pulse output will be active high when
the J0 byte is presented on the POUT[7:0]A data
bus. Figure 6 depicts the functional timing of this
signal.
An Out-of-Frame (OOF) also known as an SEF con-
dition on an STS-48/STM-16 signal will be declared
when a minimum of four consecutive errored framing
patterns have been received. The maximum SEF de-
tection time will be 625 µs for a random signal. The
framing algorithm used to check the alignment is
such that 10-3 BER does not cause an SEF more
than once every 6 minutes. This algorithm examines
the 48th A1 (F6h) byte and the first four bits of the
first A2 (28h) byte for a total of 12 bits to guarantee
this requirement.
FP Frame Pulse
The FP output indicates frame boundaries in the in-
coming data stream. FP pulses high for one POCLK
cycle when the third A2 byte of the framing se-
quence is valid on the POUT[7:0]A data bus. Figure
7 depicts the functional timing of this signal.
STS-48/STM-16 Byte Interleave Demux
When in an SEF condition the S3045 will assume
the frame has been recovered and declare an in-
frame condition on detecting two successive error-
free framing patterns. This implementation of the
frame recovery circuit achieves realignment follow-
ing a declared SEF within 250-µs.
The byte interleave demux shown in Figure 2 con-
verts the byte wide STS-48/STM-16 data stream into
four byte wide STS-12/STM-4 data streams. The
data is byte de-interleaved using four bytes at a
time. The data is output with a 77.76 MHz clock.
Figure 5. OOF State Machine
4 consecutive errored framing patterns
Reset
OOF (SEF)
STATE
NORMAL STATE
2 consecutive error free
framing patterns
8
December 13, 1999 / Revision E
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
