VSC6134
Datasheet
2.7.7
Forward Error Correction
Add path encoding is one of the following:
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Standard G.975 Reed Solomon FEC encoding.
Vitesse proprietary enhanced FEC encoding.
Selecting one type of encoding puts the other encoder in a lower power state by pumping zeros into its
data input. Global configuration bit FEC_MODE_E selects between the two modes.
For the drop path, only the standard G.975 Reed Solomon FEC encoding is provided.
2.7.7.1
Reed Solomon Encoding
Deinterleaving Buffer
The deinterleaving buffer performs the 16-byte-deinterleaving of the FEC frames to produce the
239 symbols of data and placeholders for the 16 parity symbols of the 255-symbol Reed Solomon
codewords. This is according to ITU-T G.709 recommendation.
Table 35. Deinterleaving Buffer Block I/O Description
Name
Direction
IN
Function
tx_resetn
tx_clk
Transmit reset.
IN
Transmit clock.
nfa
IN
New frame alignment.
OTUk overhead marker. (Unused.)
Data In is the OTUk frame with placeholders for the RS parity bytes.
New frame alignment out.
OTUk overhead marker out.
OTUk frame start out.
Read address out.
fstartin
IN
data_in[63:0]
nfa_out
IN
OUT
OUT
OUT
OUT
OUT
OUT
fsyncout
fstartout
rdaddrout
wraddrout
data_out[63:0]
Write address out.
Data out.
Reed Solomon Encoder
The block is designed for high-performance applications and is configured for code block length of
255 8-bit symbols with parity length of 16 8-bit symbols. It is capable of processing continuous
10-gigabit data streams in real-time.
The code generator polynomial coefficients, the codeword length, and the parity length are preset to
meet G.975 and G.709 recommendations requirements.
The RS encoder block consists of eight synchronized RS encoder blocks provided by Integrated Silicon
System (ISS). Each block has a byte-wide data interface and operates on one FEC subframe at a time.
The block diagram in the following figure shows the main functional blocks and interfaces of each Reed
Solomon encoder with the data inputs and outputs.
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VMDS-10185 Revision 4.0
July 2006
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
