Ports And Attributes; Txbypass8B10B, Rx_Decode_Use - Xilinx RocketIO User Manual

Product Not Recommended for New Designs
8B/10B Encoding/Decoding

Ports and Attributes

TXBYPASS8B10B,
RX_DECODE_USE
One port and one attribute enable 8B/10B encoding/decoding in the transceiver.
TXBYPASS8B10B is a byte-mapped port that is 1, 2, or 4 bits wide, depending on the data
width of the transceiver primitive being used. These bits correlate to each byte of the data
path. To enable 8B/10B encoding in the transmitter, these bits must be set Low. In this
mode, the transmit data input to the TXDATA port is non-encoded data of either 8, 16, or
32 bits wide. However, if other encoding schemes are preferred, the encoder capabilities
can be bypassed by setting all bits High. In this mode, the data input to TXDATA is either
10, 20, or 40 bits wide. The extra bits are fed through the TXCHARDISPMODE and
TXCHARDISPVAL buses (shown in
The decoder is controlled by the attribute RX_DECODE_USE. When this attribute is set to
TRUE, the decoder is enabled and should coincide with TXBYPASS8B10B being set Low. In
this mode, the received data output from the RXDATA port is decoded data, either 8, 16, or
32 bits wide. However, when the attribute is set to FALSE, the decoder is disabled. In this
mode, the received data is 10, 20, or 40 bits wide, and the extra bits are provided by
RXCHARISK and RXRUNDISP (shown in
If this pair is not matched, the data is not received correctly.
encoding/decoding blocks of the transceiver and how the data passes through these
blocks.
on whether 8B/10B is bypassed or enabled.
32/16/8 bits
TXDATA
50 – 156.3 MHz
32/16/8 bits
RXDATA
RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
Table 2-10 shows the significance of 8B/10B ports that change purpose depending
Transceiver Module
Physical Coding Sublayer
F
C
8B/10B I
R
F
Encode
C
O
REFCLK
Channel Bonding
and
Clock Correction
CRC
8B/10B
Elastic
Decode
Buffer
Comma Detect
Figure 2-12: 8B/10B Data Flow
www.xilinx.com
Table 2-10).
Table 2-10).
Figure 2-12
Physical Media Attachment
Mindspeed IP
Transmit
Serializer
Buffer
TX Clock Generator
Transmitter
20X Multiplier
Receiver
RX Clock Recovery
Receive
Deserializer
Buffer
R
shows the
TX+
TX−
RX+
RX−
UG024_09_020507
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