Xilinx Virtex-5 RocketIO GTP User Manual

Virtex-5 RocketIO GTP Transceiver User Guide www.xilinx.com 159
UG196 (v1.3) May 25, 2007
Configurable 8B/10B Decoder
R
K Characters and 8B/10B Commas
The 8B/10B table (shown in Appendix C) includes special characters (K characters) that
are often used for control functions. When RXDATA is a K character, the decoder drives
RXCHARISK High.
If DEC_PCOMMA_DETECT is TRUE, the decoder drives RXCHARISCOMMA High
whenever RXDATA is a positive 8B/10B comma. Likewise, if DEC_MCOMMA_DETECT
is TRUE, the decoder drives RXCHARISCOMMA High whenever RXDATA is a negative
8B/10B comma.
To limit the set of commas that trigger RXCHARISCOMMA to K28.1, K28.5, and K28.7,
DEC_VALID_COMMA_ONLY is set to TRUE. This setting is typically used for Ethernet-
based applications. RXCHARISCOMMA does not depend on MCOMMA_10B_VALUE or
PCOMMA_10B_VALUE.
RX Running Disparity
8B/10B uses a running disparity system to balance the number of 1s and 0s transmitted.
The 8B/10B decoder tracks the running disparity of incoming data to detect errors.
Monitor the RXRUNDISP port to see the current running disparity.
Disparity Errors and Not-in-Table Errors
The decoder drives RXDISPERR High when RXDATA arrives with the wrong disparity. In
addition to disparity errors, the 8B/10B decoder detects illegal 10-bit codes (out-of-table
errors). The decoder drives the RXNOTINTABLE port High when RXDATA is not a valid
8B/10B character.
Figure 7-18: RX Interface with 8B/10B Decoding
1514131211109876543210
H
1
G
1
F
1
E
1
D
1
C
1
B
1
A
1
H
0
G
0
F
0
E
0
D
0
C
0
B
0
A
0
H
0
G
0
F
0
E
0
D
0
C
0
B
0
A
0
76543210
RXDATAWIDTH = 1
RXDATA
RXDATAWIDTH = 0
UG196_c7_18_102306
Received
Last
Received
Last
Received
First
Received
First
8B/10B
g
0
h
0
j
0
f
0
i
0
e
0
d
0
c
0
b
0
a
0
g
0
h
0
j
0
f
0
i
0
e
0
d
0
c
0
b
0
a
0
g
1
h
1
j
1
f
1
i
1
e
1
d
1
c
1
b
1
a
1
8B/10B

Xilinx Virtex-5 RocketIO GTP Specifications

General

Brand	Xilinx
Model	Virtex-5 RocketIO GTP
Category	Transceiver
Language	English