Altera Corporation
2–187
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
Figure 2–137
shows the SONET/SDH frame structure.
Figure 2–137. SONET/SDH Frame Structure
Note to
Figure 2–137
(1)
N=12 for OC-12, 48 for OC-48, and 96 for OC-96.
Transport overhead bytes A1 and A2 are used for recovering the frame
boundary from the serial data stream. Frame sizes are fixed, so the A1 and
A2 bytes appear within the serial data stream every 125
μ
s. In an OC-12
backplane system, twelve A1 bytes are followed by twelve A2 bytes.
Similarly, in an OC-48 backplane system, forty-eight A1 bytes are
followed by forty-eight A2 bytes.
In SONET/SDH systems, byte values of A1 and A2 are fixed as follows:
■
A1 = “11110110” or 8'hF6
■
A2 = “00101000” or 8'h28
OC-12 and OC-48 Data Paths
OC-12 and OC-48 configurations have similar data paths, as seen in
Figures 2–138
and
2–139
. The only difference is that OC-48 has a 16-bit
PLD interface as compared to the 8-bit PLD interface in an OC-12
configuration. The OC-48 configuration employs the byte serializer and
deserializer and a byte ordering block to translate 16-bit PLD interfaces
into an 8-bit transceiver data path.
NxA1
NxA2
NxJ0/Z0
9 Rows
Nx3 Bytes
Transport Overhead
Nx3 Bytes
Payload