8B/10B Serial Output Format; Hdl Code Examples: Transceiver Bypassing Of 8B/10B Encoding - Xilinx RocketIO User Manual

8B/10B Encoding/Decoding

8B/10B Serial Output Format

The 8B/10B encoding translates a 8-bit parallel data byte to be transmitted into a 10-bit serial data
stream. This conversion and data alignment are shown in
least significant bit of the 10-bit data "a" first and proceeds to "j". This allows data to be read and
matched to the form shown in
The serial data bit sequence is dependent on the width of the parallel data. The most significant byte
is always sent first, regardless of the whether 1-byte, 2-byte, or 4-byte paths are used. The least
significant byte is always last.
byte of the parallel data. TXDATA [31:24] is serialized and sent out first, followed by TXDATA
[23:16], TXDATA [15:8], and finally TXDATA [7:0]. The 2-byte path transmits TXDATA [15:8]
and then TXDATA [7:0].

HDL Code Examples: Transceiver Bypassing of 8B/10B Encoding

8B/10B encoding can be bypassed by the transceiver. The TXBYPASS8B10B is set to 1111; the
RXDECODE attribute is set to FALSE to create the extra two bits needed for a 10-bit data bus; and
TXCHARDISPMODE, TXCHARDISPVAL, RXCHARISK, and RXRUNDISP are added to the 8-
bit data bus.
Please use the Architecture Wizard to create instantiation templates. This wizard creates code and
instantiation templates that define the attributes for a specific application.
RocketIO™ Transceiver User Guide
UG024 (v2.3.2) June 24, 2004
Appendix B, "8B/10B Valid Characters."
H G F
7 6 5
Parallel
a b c
0 1 2
Serial
First transmitted
Figure 2-15: 8B/10B Parallel to Serial Conversion
Figure 2-16
H 3 − A 3 H 2 − A 2
TXDATA 31:24 TXDATA 23:16
a 3 − j 3 a 2 − j 2
LSB 3 LSB 2
1 st Sent 2 nd Sent
Encoded Encoded
Figure 2-16: 4-Byte Serial Structure
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Figure 2-15. The serial port transmits the
E D C B A
4 3 2 1 0
8B/10B
d e i f g
3 4 5 6 7
Last transmitted
shows a case when the serial data corresponds to each
H 1 − A 1
TXDATA 15:8
8B/10B
a 1 − j 1
LSB 1 LSB 0
3 rd Sent
Encoded
h j
8 9
UG024_10_021102
H 0 − A 0
TXDATA 7:0
a 0 − j 0
4 th Sent
Encoded
U024_11_020802
67
R