Rx Running Disparity - Xilinx 7 Series User Manual

Chapter 4: Receiver
transceiver always receives the right-most bit first. Consequently, the 8B/10B decoder automatically
reverses the bit order of received data before decoding it. Decoded data is available on RXDATA
ports.
or 40. Data is reconstructed into bytes and sent to the RXDATA interface after the 8B/10B decoder.
The number of bits used by RXDATA and corresponding byte orders are determined by
RX_DATA_WIDTH.
•
•
When the 8B/10B decoder is bypassed but RX_DATA_WIDTH is set to multiple of 10, 10-bit
characters are passed to the RX data interface with this format:
•
•
•
X-Ref Target - Figure 4-33
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8
RXDATA H3 G3 F3 E3 D3 C3 B3 A3 H2 G2 F2 E2 D2 C2 B2 A2 H1 G1 F1 E1 D1 C1 B1 A1 H0 G0 F0 E0 D0 C0 B0 A0
j3 h3 g3 f3 i3 e3 d3 c3 b3 a3 j2 h2 g2 f2 i2 e2 d2 c2 b2 a2 j1 h1 g1 f1 i1 e1 d1 c1 b1 a1 j0 h0 g0 f0 i0 e0 d0 c0 b0 a0
Received
Last

RX Running Disparity

Disparity check is performed and the decoder drives the corresponding RXDISPERR High when the
data byte on 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 decoder is enabled but a received 10-bit character cannot be mapped into a valid 8B/10B
character listed in
out of the decoder through the RX data interface with this format:
170
Send Feedback
Figure 4-33 shows data received by the GTP transceiver RX when RX_DATA_WIDTH = 20
Only use RXDATA[15:0] if RX_DATA_WIDTH = 20
Use full RXDATA[31:0] if RX_DATA_WIDTH = 40
The corresponding RXDISPERR represents the 9th bit
The corresponding RXCHARISK represents the 8th bit
The corresponding RXDATA byte represents the [7:0] bits
RX_DATA_WIDTH = 20
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RXDATA H1 G1 F1 E1 D1 C1 B1 A1 H0 G0 F0 E0 D0 C0 B0 A0
MSB
j1 h1 g1 f1 i1 e1 d1 c1 b1 a1 j0 h0 g0 f0 i0 e0 d0 c0 b0 a0
Received
Last
RX_DATA_WIDTH = 40
Figure 4-33: 8B/10B Decoder Bit and Byte Order
Appendix C, 8B/10B Valid
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8B/10B
Received
7 6 5 4 3 2 1 0
8B/10B
Characters. The non-decoded 10-bit character is piped
7 Series FPGAs GTP Transceivers User Guide
LSB
First
MSB
Received
UG482_c4_22_111011
UG482 (v1.9) December 19, 2016
LSB
First