Xilinx Virtex-5 RocketIO GTP User Manual

Virtex-5 RocketIO GTP Transceiver User Guide www.xilinx.com 113
UG196 (v1.3) May 25, 2007
Configurable TX Driver
R
Ports and Attributes
Table 6-15 defines the TX driver ports.
Table 6-16 defines the TX driver attributes.
Description
Differential Voltage Control
The amplitude of the TX driver’s differential swing can be controlled using the
TXDIFFCTRL and TXBUFDIFCTRL ports. As shown in Figure 6-14, page 112,
TXDIFFCTRL controls the drive strength of the main pad driver and the pre-emphasis pad
driver. Table 6-17 shows the differential output voltage that results from each of the
possible settings for the port. Table 6-18 shows the expected transmitter pre-emphasis a
percentage of overall TX swing.
Table 6-15: TX Driver Ports
Ports Dir
Clock
Domain
Description
MGTTXN0
MGTTXN1
MGTTXP0
MGTTXP1
Out
(Pad)
TX Serial
Clock
TXN and TXP are the differential
complements of each other forming a
differential transmitter output pair. These
ports represent pads, so their locations
must be constrained (see Chapter 4,
“Implementation”), and they must be
brought to the top level of the design.
TXBUFDIFFCTRL0[2:0]
TXBUFDIFFCTRL1[2:0]
In Async
Controls the strength of the pre-drivers.
This port should be tied to the same value
as the TXDIFFCTRL port for the
transceiver.
TXDIFFCTRL0[2:0]
TXDIFFCTRL1[2:0]
In Async
Controls the transmitter differential
output swing. Table 6-18 shows the
approximate differential voltage swing
that results from each setting.
TXPREEMPHASIS0[2:0]
TXPREEMPHASIS1[2:0]
In Async
Controls the relative strength of the main
drive and pre-emphasis as shown in
Table 6-18.
Table 6-16: TX Driver Attributes
Attribute Description
TX_DIFF_BOOST0
TX_DIFF_BOOST1
Changes the strength of the TX driver and pre-emphasis buffers.
When set to FALSE, the pre-emphasis percentage is boosted or
increased. See Table 6-18, page 114 for nominal differential swing
and pre-emphasis values.
Overall differential swing is reduced when TX_DIFF_BOOST is
TRUE (default setting).

Xilinx Virtex-5 RocketIO GTP Specifications

General

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