8B/10B Decoder in Single-Width Mode
In single-width mode, the 8B/10B decoder decodes the received 10-bit code groups into an 8-bit data and a
1-bit control identifier, in compliance with Clause 36 in the IEEE 802.3 specification. The 1-bit control
identifier indicates if the decoded 8-bit code is a valid data or special control code. The decoded data is fed
to the byte deserializer or the receiver phase compensation FIFO (if the byte deserializer is disabled).
Figure 1-28: 8B/10B Decoder in Single-Width Mode
datain[9:0]
dataout[7:0]
control identifier
error status
8B/10B Decoder
8B/10B Decoder in Double-Width Mode
In double-width mode, two 8B/10B decoders are cascaded to decode the 20-bit code groups into two sets of
8-bit data and two 1-bit control identifiers. When receiving the 20-bit code group, the 10-bit LSByte is
decoded first and the ending running disparity is forwarded to the other 8B/10B decoder for decoding the
10-bit MSByte.
Figure 1-29: 8B/10B Decoder in Double-Width Mode
datain[19:10]
dataout[15:8]
control identifier
error status
8B/10B Decoder
(MSByte Decoding)
datain[9:0]
dataout[7:0]
control identifier
error status
8B/10B Decoder
(LSByte Decoding)
Current Running Disparity
Control Code Group Detection
The 8B/10B decoder indicates whether the decoded 8-bit code group is a data or a control code group on
the
rx_datak
signal. If the received 10-bit code group is one of the 12 control code groups (
/Kx.y/
)
specified in the IEEE802.3 specification, the
rx_datak
signal is driven high. If the received 10-bit code
group is a data code group (
/Dx.y/
), the
rx_datak
signal is driven low.
Transceiver Architecture in Cyclone V Devices
Altera Corporation
CV-53001
8B/10B Decoder in Single-Width Mode
1-44
2013.05.06