Xilinx RocketIO User Manual

RocketIO™ Transceiver User Guide www.xilinx.com 91
UG024 (v3.0) February 22, 2007
Miscellaneous Signals
R
TERMINATION_IMP
Receive Termination
On-chip termination is provided at the receiver, eliminating the need for external
termination. The receiver includes programmable on-chip termination circuitry for 50Ω
(default) or 75Ω impedance.
Transmit Termination
On-chip termination is provided at the transmitter, eliminating the need for external
termination. Programmable options exist for 50Ω (default) and 75Ω termination.
TXPOLARITY,
RXPOLARITY,
TXINHIBIT
A differential pair has a positive-designated and a negative-designated component. If for
some reason the polarity of these components is switched between two transceivers, the
data will not be passed properly. If this occurs, TXPOLARITY will invert the definition of
the TXN and TXP pins. On the receiver side of the MGT, the RXPOLARITY port can invert
the definition of RXN and RXP.
For some protocols, the MGT must turn off the TXN/TXP pins. The TXINHIBT port shuts
off the transmit pins and forces them to a constant value (TXN = 0, TXP = 1). Asserting
TXINHIBIT also disables internal serial loopback.
TX_DIFF_CTRL,
PRE_EMPHASIS
These two attributes control analog functionality of the MGT.
The TX_DIFF_CTRL attribute is used to compensate for signal attenuation in the link
between transceivers. It has five possible values of 400, 500, 600, 700, and 800 mV. These
values represent the peak-to-peak amplitude of one component of the differential pair; the
full differential peak-to-peak amplitude is two times these values.
The PRE_EMPHASIS attribute has four values—10%, 20%, 25%, and 33%—which are
designated by 0, 1, 2, and 3 respectively. Pre-emphasis is discussed in greater detail in
Chapter 3, “Analog Design Considerations.”
LOOPBACK
To facilitate testing without the requirement to apply patterns or measure data at gigahertz
rates, two programmable loopback features are available.
One option, serial loopback, places the gigabit transceiver into a state where transmit data
is directly fed back to the receiver. An important point to note is that the feedback path is
at the output pads of the transmitter. This tests the entirety of the transmitter and receiver.
Table 2-22: Serial Speed Ranges as a Function of SERDES_10B
SERDES_10B Reference Clock Range Serial Speed Range
TRUE 60 – 100 MHz 600 Mb/s – 1.0 Gb/s
FALSE 50 – 156.25 MHz 1.0 Gb/s – 3.125 Gb/s
Product Not Recommended for New Designs

Xilinx RocketIO Specifications

General

Brand	Xilinx
Model	RocketIO
Category	Transceiver
Language	English