114
Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
Chapter 6:
GTP Transmitter (TX)
R
Each of the pad drivers is driven by a pre-driver whose output amplitude is controlled by
TXBUFDIFCTRL. Although the pre-driver output swing does not change the output swing
at the TX pad, the inputs of TXBUFDIFCTRL and TXDIFFCTRL must always be tied
together.
Each GTP transceiver includes an additional attribute, TX_DIFF_BOOST, which can be
used to increase the maximum possible output swing. TX_DIFF_BOOST is set to FALSE
when additional output swing is required. TX_DIFF_BOOST is set to TRUE when the
output swing is acceptable and lower power consumption is desired.
Pre-Emphasis
Serial traces tend to attenuate high frequencies more than low frequencies. Pre-emphasis is
a technique used to equalize transmitted data. It compensates for the excess high-
frequency loss by transmitting high-frequency signals with more power than low-
frequency signals.
Table 6-17:
Transmitter Output Swing
Port
Value
Transmitter Differential Swing (mV)
TXDIFFCTRL0[2:0] = TXBUFDIFFCTRL0[2:0]
TXDIFFCTRL1[2:0] = TXBUFDIFFCTRL1[2:0]
000
1100
001
1050
010
1000
011
900
100
800
101
600
110
400
111
0
Table 6-18:
Transmitter Pre-Emphasis Settings
Port
Value
Transmitter Pre-Emphasis (%)
(1,2)
TXPREEMPHASIS0[2:0]
TXPREEMPHASIS1[2:0]
Pre-Emphasis Boost On
TX_DIFF_BOOST = FALSE
Pre-Emphasis Boost Off
TX_DIFF_BOOST = TRUE (Default Setting)
000
2
3
001
2
3
010
2.5
4
011
4.5
10.5
100
9.5
18.5
101
16
28
110
23
39
111
31
52
Notes:
1. Nominal values. Refer to the
Virtex-5 Data Sheet
for the exact values.
2. Refer to
, pages 211-215 and
, pages 465-471 for detailed explanations of pre-emphasis.
Содержание Virtex-5 RocketIO GTP
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Страница 256: ...256 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Section 3 Appendices R...
Страница 312: ...312 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Appendix E Low Latency Design R...