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K Characters and 8B/10B Commas
The 8B/10B table (shown in
are often used for control functions. When RXDATA is a K character, the decoder drives
RXCHARISK High.
If DEC_PCOMMA_DETECT is TRUE, the decoder drives RXCHARISCOMMA High
whenever RXDATA is a positive 8B/10B comma. Likewise, if DEC_MCOMMA_DETECT
is TRUE, the decoder drives RXCHARISCOMMA High whenever RXDATA is a negative
8B/10B comma.
To limit the set of commas that trigger RXCHARISCOMMA to K28.1, K28.5, and K28.7,
DEC_VALID_COMMA_ONLY is set to TRUE. This setting is typically used for Ethernet-
based applications. RXCHARISCOMMA does not depend on MCOMMA_10B_VALUE or
PCOMMA_10B_VALUE.
RX Running Disparity
8B/10B uses a running disparity system to balance the number of 1s and 0s transmitted.
The 8B/10B decoder tracks the running disparity of incoming data to detect errors.
Monitor the RXRUNDISP port to see the current running disparity.
Disparity Errors and Not-in-Table Errors
The decoder drives RXDISPERR High when RXDATA arrives with the wrong disparity. In
addition to disparity errors, the 8B/10B decoder detects illegal 10-bit codes (out-of-table
errors). The decoder drives the RXNOTINTABLE port High when RXDATA is not a valid
8B/10B character.
Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
RXDATAWIDTH = 1
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Figure 7-18: RX Interface with 8B/10B Decoding
www.xilinx.com
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Appendix
C) includes special characters (K characters) that
Configurable 8B/10B Decoder
RXDATAWIDTH = 0
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UG196_c7_18_102306
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