SBI Bus Serializer ASSP Telecom Standard Product Data Sheet
Released
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2000168, Issue 5
75
10.7.2
PRBS Detector
The PRBS detector sub-block monitors the synchronous payload envelope, SPE, bytes in the
incoming data stream. The incoming data is compared against the expected value derived from
an internal linear feedback shift register (LFSR) with a polynomial of X
23
+ X
18
+ 1. If the
incoming data fails to match the expected value for three consecutive bytes, the PRBS detector
sub-block will enter out-of-synchronization (OOS) state. The LFSR will be re-initialized using
the incoming data bytes. The new LFSR seed is confirmed by comparison with subsequent
incoming data bytes. The PRBS detector sub-block will exit the OOS state when the incoming
data matches the LFSR output for three consecutive bytes. The PRBS detector sub-block will
remain in the OOS state and re-load the LFSR if confirmation failed. The PRBS sub-block
counts PRBS byte errors and optionally generates interrupts when it enters and exits the OOS
state.
10.8 Transmit 8B/10B Encoders
The Transmit 8B/10B Encoder blocks, TW8E and TP8E, construct an 8B/10B character stream
from an incoming translated SBI336 bus or Telecom bus carrying an STS-12/STM-4 equivalent
stream.
In SBI mode, these blocks encode the SBI336S stream as shown in Table 21. When configured
for Synchronous mode for DS0 switching, the 8B/10B encoder transmits CAS signaling multi-
frame alignment across the SBI336S interface by generating a C1FP character every 48 frame
times. When not configured for DS0 switching the C1FP character is sent every 4 frames.
10.8.1
SBI336S 8B/10B Character Encoding
Table 21 shows the mapping of SBI336S bus control bytes and signals into 8B/10B control
characters. The linkrate octet in location V4, V1 and V2, the in-band programming channel, the
V3 octet when it contains data are all carried as data. Justification requests for master timing are
carried in the V5 character so there are three V5 characters used, nominal, negative timing
adjustment request, and positive timing adjustment request.
Table 21 SBI336S Character Encoding
Code Group
Name
Curr. RD-
abcdei fghj
Curr. RD+
abcdei fghj
Encoded Signals
Description
Common to All Link Types
K28.5
001111 1010
110000 0101
IC1FP=’b1
C1FP frame and multi-frame alignment
K23.7-
111010 1000
-
Overhead Bytes (columns 1-60 or 1-72
except for C1 and in-band programming
channel), V3 or H3 byte except during
negative justification, byte after V3 or H3
byte during positive justification, unused
bytes in fraction rate links
Asynchronous T1/E1 Links
K27.7-
110110 1000
-
V5 byte, no justification request
K28.7-
001111 1000
-
V5 byte, negative justification request