Rx Running Disparity - Xilinx Virtex-6 FPGA User Manual

RX Running Disparity

8B/10B includes special characters (K characters) that 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. Similarly, if DEC_MCOMMA_DETECT
is TRUE, the decoder drives RXCHARISCOMMA High whenever RXDATA is a negative
8B/10B comma.
The decoder drives RXDISPERR High when RXDATA arrives with the wrong disparity. In
addition to disparity errors, the 8B/10B decoder detects 20-bit out-of-table error codes. The
decoder drives the RXNOTINTABLE port High when RXDATA is not a valid 8B/10B
character.
Figure 4-30
RXNOTINTABLE and RXDISPERR ports indicating the error.
X-Ref Target - Figure 4-30
RXNOTINTABLE
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Virtex-6 FPGA GTX Transceivers User Guide
UG366 (v2.5) January 17, 2011
shows a waveform with a few error bytes arriving on RXDATA and the
RXUSRCLK2
Good
RXDATA
Data
RXDISPERR
Figure 4-30: RX Data with 8B/10B Errors
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Disp Out of Both
Error Table Errors
RX 8B/10B Decoder
Good
Data
UG366_c4_27_051509
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