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Chapter 10: GTP-to-Board Interface
Table 10-1: Analog Pins (Continued)
Table 10-2
Table 10-2: Analog Attributes
Description
Each Virtex-5 LXT or SXT device requires one 50 Ω external precision (1%) resistor on the
PCB (connected directly to the MGTRREF pin and to the closest MGTAVTTTX pin).
Each used GTP_DUAL tile requires a filter circuit on the following analog power supply
pins:
•
•
•
•
The correct implementation and placement of these filter circuits is important for
suppressing high-frequency noise.
Figure 10-1
and MGTAVTTTX pins of the device. The nominal 50 Ω value can be closely matched with
a 49.9 Ω resistor with 1% tolerance. Each LXT or SXT device requires a filter circuit on the
MGTAVTTRXC pin, which powers the resistor calibration circuit of the device.
202
Pins
MGTAVTTTX
MGTREFCLKP
MGTREFCLKN
MGTRREF
defines the analog attributes.
Attribute
TERMINATION_CTRL[4:0]
TERMINATION_OVRD
TERMINATION_IMP_0
TERMINATION_IMP_1
MGTAVCCPLL
MGTAVTTTX
MGTAVTTRX
MGTAVCC
illustrates the connection of the external precision resistor to the MGTRREF
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MGTAVTTTX is the analog supply for the transmitter
In
termination and driver circuits of the GTP_DUAL tile.
Differential clock input pin pair for the reference clock of
In
the GTP_DUAL tile.
MGTRREF is the reference resistor input for the entire
In
device.
Controls the internal termination calibration circuit. Refer to
Table 10-3, page 206
for encoding.
Selects whether the external 50Ω precision resistor connected
to the MGTRREF pin or an override value is used, as defined
by TERMINATION_CTRL[4:0].
Selects the termination impedance for the TX driver and RX
receiver.
See
Figure 10-5
calibrating the impedance values. Always set
to 50, which selects the 50Ω termination impedance.
Virtex-5 RocketIO GTP Transceiver User Guide
Description
Description
UG196 (v1.3) May 25, 2007
R
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