QT2022/32 - Data Sheet: DS3051
7.2.5 Descrambler
The descrambler processes the frame to reverse the effect of the scrambler using the same polynomial as scram-
bler, with the exception of the A1,A2,J0 and Z0 octets (576 octets in total, per WIS frame), which bypass the
descrambler.
7.2.6 Section Overhead Extraction and B1 Check
Section Overhead extraction extracts J0, Z0 and B1 and also removes the Section Overhead from the input data
stream.The J0 and Z0 will be bypassed by the descrambler. The J0 octet is passed to the Station Management
entity (MDIO block) via a specific register (J0 RX register).
The B1 octet is a bit-interleaved parity 8 code using even parity. It is extracted from the incoming WIS frame after
the descrambler. The B1 octet is stored and compared with the calculated B1 of the previous frame. The B1 check
performs the B1 calculation of the incoming WIS frame before descrambling and also performs the comparison
between the calculated B1 octet and the received B1 octet extracted from the incoming frame.
7.2.7 Line Overhead Extraction, Pointer (H1,H2) Process, and B2 Check
Line Overhead extraction removes the H1, H2, H3, B2, K1, K2, S1 and M1 octets and also the Line Overhead from
the WIS stream which does not include the Section Overhead. The M1 octet is passed to the MDIO block via a spe-
cific register (WIS M1 register).
RDI-L (Line Remote Defect Indication) signal is asserted by a 110 code in bit positions 6,7 and 8 of the K1 octet.
And RDI-L signal is de-asserted by any code other than the 110 code in the bits 6,7 and 8 of K2 octet. The RDI-L is
passed to the Station Management entity (MDIO block) via a specific register. The Pointer (H1,H2) process uses
the H1 and H2 taken from Line Overhead extraction. The pointer marks the beginning of the STS-192c SPE. It also
indicates a concatenated payload. The two bytes (H1,H2) allocated to the pointer function can be viewed as one
word as shown in Figure 12. The last ten bits (bit 7-16) of the pointer word carry the pointer value.
Figure 12: STS-1 Payload pointer (H1, H2, H3) coding
H1
H2
H3
1
2
3
4 5
6
7
8
9 10 11 12 13 14 15 16
N N N N
I
D I D I D I D I
D
0 1
1
0
0
0
10 BIT POINTER
NEW DATA FLAG -- INVERT 4 N BITS
NEGATIVE STUFF -- INVERT 5 D BITS
POSITIVE STUFF -- INVERT 5 I BITS
I - Increment Bit
D - Decrement Bit
N - New Data Flag Bit
POSITIVE
STUFF
OPPORTUNITY
NEGATIVE
STUFF
OPPORTUNITY
Revision 5.11
AppliedMicro - Confidential & Proprietary
43
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
