S3045
SONET/SDH OC-12 TO OC-48 MUX/DEMUX
single STS-48/STM-16 frame). The B1 parity byte is
calculated after the M1 bytes are inserted, the sec-
tion-trace J0/Z0 bytes are inserted, and the B2 parity
bytes are inserted.
frame). These parity bytes are optionally calculated
and inserted after the M1 bytes are inserted into the
STS-48/STM-16 and before the B1 is calculated and
inserted. The B2/M1SELB select line allows for B2
and M1 calculations to be turned off.
B2 Parity Calculation
M1 Byte ( B2 Parity Error Count )
The B2 byte is allocated in each STS-1 frame for a
line error monitoring function. The interleave even
parity byte B2 is optionally calculated and inserted
only over the four STS-1 frames that the four M1
bytes were inserted (the B2 byte will not be calculated
for all 48 STS-1’s). These four B2 bytes are calcu-
lated over the STS-1 frames of the previous STS-48/
STM-16 frame except for the first three rows of the
section overhead (computed over all bits of the line
overhead and capacity envelope of the previous STS-
1 frame before scrambling) and is inserted into the
appropriate B2 locations (locations of the B2 bytes
are found by control from the frame counter block) of
the current frame before scrambling. These bytes will
be inserted within a STS-48/STM-16 signal (48 B2
bytes are contained in a single STS-48/STM-16
The STS-48/STM-16 M1 byte is calculated by ex-
tracting each of the four M1 bytes of the STS-12/
STM-4 frames and adding them together and insert-
ing this new M1 byte into the STS-48/STM-16 M1
byte. For STS-48/STM-16 rate the M1 count will
truncate at 255 (never report more than 255 errors).
The STS-48/STM-16 M1 byte will only be transmitted
over the number one STS-12/STM-4 data stream.
The other 3 STS-12/STM-4 M1 bytes will be inserted
with the value of zero.
Section-trace Insertion (J0/Z0) Bytes
The section-trace bytes (J0/Z0) can optionally be
filled by setting J0/Z0SEL as indicated below in
Table 1.
Table 1. Section-Trace Insertion (J0/Z0) Bytes
J0/Z0SEL
Description
0
Transparent Operation - J0/Z0 bytes are passed through with no modification.
Byte 1 of 48 (J0 byte) is passed through with no modification (transparent) and
bytes 2 through 48 (Z0 bytes) are filled with the values of 02hex to 30hex (48
decimal) respectively.
1
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December 13, 1999 / Revision E
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
