Xilinx RocketIO User Manual

62 www.xilinx.com RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
Chapter 2: Digital Design Considerations
R
TXCHARDISPVAL,
TXCHARDISPMODE
TXCHARDISPVAL and TXCHARDISPMODE are dual-purpose ports for the transmitter
depending upon whether 8B/10B encoding is enabled. Table 2-10 shows this dual
functionality. When encoding is enabled, these ports function as byte-mapped control
ports controlling the running disparity of the transmitted serial data.
In the encoding configuration, the disparity of the serial transmission can be controlled
with the TXCHARDISPVAL and TXCHARDISPMODE ports. When TXCHARDISPMODE
is set High, the running disparity is set before encoding the specific byte.
TXCHARDISPVAL determines if the disparity is negative (set Low) or positive (set High).
Table 2-11 illustrates this.
Table 2-10: 8B/10B Bypassed Signal Significance
Function
TXBYPASS8B10B
0
8B/10B encoding is enabled (not bypassed). 1, 2, or 4 bits, mapped to number of
bytes of data path width.
1
8B/10B encoding bypassed (disabled). 1, 2, or 4 bits, mapped to number of bytes
of data path width.
Function, 8B/10B Enabled Function, 8B/10B Bypassed
TXCHARDISPMODE,
TXCHARDISPVAL
00 Maintain running disparity normally
Part of 10-bit encoded byte
(see Figure 2-13):
TXCHARDISPMODE[0]
(or: [1] / [2] / [3])
TXCHARDISPVAL[0]
(or: [1] / [2] / [3])
TXDATA[7:0]
(or: [15:8] / [23:16] / [31:24])
01
Invert the normally generated running
disparity before encoding this byte.
10
Set negative running disparity before
encoding this byte.
11
Set positive running disparity before
encoding this byte.
RXCHARISK Received byte is a K-character Part of 10-bit encoded byte
(see Figure 2-14):
RXCHARISK[0]
(or: [1] / [2] / [3])
RXRUNDISP[0]
(or: [1] / [2] / [3])
RXDATA[7:0]
(or: [15:8] / [23:16] / [31:24])
RXRUNDISP
0
Indicates running disparity is
NEGATIVE
1
Indicates running disparity is
POSITIVE
RXDISPERR Disparity error occurred on current
byte
Unused
TXCHARISK Transmitted byte is a K-character Unused
RXCHARISCOMMA Received byte is a comma Unused
Product Not Recommended for New Designs

Xilinx RocketIO Specifications

General

Brand	Xilinx
Model	RocketIO
Category	Transceiver
Language	English