Digilent 6003-410-000P-KIT - Manual (Page 69)

XUP Virtex-II Pro Development System www.xilinx.com 69
UG069 (v1.0) March 8, 2005
Using the Multi-Gigabit Transceivers R
The RocketIO MGTs utilize differential signaling between the transmit and receive data
ports to minimize the effects of common mode noise and signal crosstalk. With the use of
high-speed serial transceivers, the interconnect media causes degradation of the signal at
the receiver. Effects such as inter-symbol interference (ISI) or data dependent jitter are
produced. This loss can be large enough to degrade the eye pattern opening at the receiver
beyond that which results in reliable data transmission. The RocketIO MGTs allow the user
to set the initial differential voltage swing and signal pre-emphasis to negate a portion of
the signal degradation to increase the reliability of the data transmission.
In pre-emphasis, the initial differential voltage swing is boosted to create a stronger rising
or falling waveform. This method compensates for high frequency loss in the transmission
media that would otherwise limit the magnitude of the received waveform.
The initial differential voltage swing and signal pre-emphasis are set by two user-defined
RocketIO transceiver attributes. The TX_DIFF_CTRL attribute sets the voltage difference
between the differential lines, and the TX_PREEMPHASIS attribute sets the output driver
pre-emphasis.
Xilinx recommends setting the TX_DIF_CTRL attribute to 600 (600 mV) and the
TXPREEMPHASIS attribute to 2 (25%) when SATA cables of 1.0 or less meters in length are
used to connect the MGT host to the MGT target. Typical eye diagrams for 1.5 Gb/s data
SATA_PORT0_IDLE – – B15 –
SATA_PORT1_TXN MGT_X1Y1 TXNPAD6 A20 TARGET
SATA_PORT1_TXP MGT_X1Y1 TXPPAD6 A19 –
SATA_PORT1_RXN MGT_X1Y1 RXNPAD6 A17 –
SATA_PORT1_RXP MGT_X1Y1 RXPPAD6 A18 –
SATA_PORT1_IDLE – – AK3 –
SATA_PORT2_TXN MGT_X2Y1 TXNPAD7 A14 HOST
SATA_PORT2_TXP MGT_X2Y1 TXPPAD7 A13 –
SATA_PORT2_RXN MGT_X2Y1 RXNPAD7 A11 –
SATA_PORT2_RXP MGT_X2Y1 RXPPAD7 A12 –
SATA_PORT2_IDLE – – C15 –
MGT_TXN MGT_X3Y1 TXNPAD9 A7 USER
MGT_TXP MGT_X3Y1 TXPPAD9 A6 –
MGT_RXN MGT_X3Y1 RXNPAD9 A4 –
MGT_RXP MGT_X3Y1 RXPPAD9 A5 –
MGT_CLK_N – – G16 BREFCLK
MGT_CLK_P – – F16 –
EXTERNAL_CLOCK_N – – F15 BREFCLK2
EXTERNAL_CLOCK_P – – G15 –
Table 2-21: SATA and MGT Signals (Continued)
Signal MGT Location PAD Name I/O Pin Notes