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

R
Table 2-11: Running Disparity Control
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
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

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.
the ports function as byte-mapped status ports for the received data.
In the 8B/10B decoding configuration, RXCHARISK asserted High indicates the received byte of
data is a control (K) character. Otherwise, the received byte of data is a data character. See
B, "8B/10B Valid
64
{TXCHARDISPMODE,
TXCHARDISPVAL}
00
01
10
11
"Vitesse Disparity Example"
Characters".
Chapter 2: Digital Design Considerations
Function
Maintain running disparity normally
Invert normally generated running disparity before encoding
this byte
Set negative running disparity before encoding this byte
Set positive running disparity before encoding this byte
below.
Table 2-10 shows this dual functionality. When decoding is enabled,
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Figure 2-13.
RocketIO™ Transceiver User Guide
UG024 (v2.3.2) June 24, 2004
Appendix