Txcharisk; Txrundisp; Txkerr; Rxcharisk, Rxrundisp - Xilinx RocketIO User Manual

Product Not Recommended for New Designs
8B/10B Encoding/Decoding
Table 2-11: Running Disparity Control
{TXCHARDISPMODE,
When TXCHARDISPMODE is set Low, the running disparity is maintained if
TXCHARDISPVAL is also set Low, but the disparity is inverted before encoding the byte
when TXCAHRDISPVAL is set High.
Most applications will use the mode where both TXCHARDISPMODE and
TXCHARDISPVAL are set Low. Some applications may use other settings if special
running disparity configurations are required, such as in the
below.
In the bypassed configuration, TXCHARDISPMODE [0] becomes bit 9 of the 10 bits of
encoded data. TXCHARDISPMODE [1:3] are bits 19, 29, and 39 in the 20- and 40-bit wide
buses. TXCHARDISPVAL becomes bits 8, 18, 28, and 38 of the transmit data. See
Figure

TXCHARISK

TXCHARISK is a byte-mapped control port that is used only when the 8B/10B encoder is
implemented. This port controls whether the byte of TXDATA is to be encoded as a control
(K) character (when asserted High) or as a data character (when de-asserted). When
8B/10B encoding is bypassed, this port is undefined.

TXRUNDISP

TXRUNDISP is a status port that is byte-mapped to TXDATA. This port indicates the
running disparity after the byte of TXDATA is encoded. When High, the disparity is
positive. When Low, the disparity is negative.

TXKERR

TXKERR is a status port that is byte-mapped to TXDATA. This port is defined only if
8B/10B encoding is enabled. If a bit is asserted High, it means that TXDATA and
TXCHARISK have combined to create an invalid control (K) character. The transmission,
reception, and decode of this invalid character will create unexpected RXDATA results in
the RocketIO receiver, or in other transceivers.
RXCHARISK,
RXRUNDISP
RXCHARISK and RXRUNDISP are dual-purpose ports for the receiver depending
whether 8B/10B decoding is enabled.
decoding is enabled, the ports function as byte-mapped status ports for the received data.
RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
TXCHARDISPVAL}
Maintain running disparity normally
00
Invert normally generated running disparity before
01
encoding this byte
Set negative running disparity before encoding this byte
10
Set positive running disparity before encoding this byte
11
2-13.
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Function
"Vitesse Disparity Example"
Table 2-10 shows this dual functionality. When
R
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