Xilinx Virtex-5 RocketIO GTP

96 www.xilinx.com Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
Chapter 6: GTP Transmitter (TX)
R
REFCLKOUT Driving Multiple Transceivers with a 2-Byte Interface
Figure 6-8 shows how REFCLKOUT can be used to generate USRCLK signals.
REFCLKOUT runs continuously, even when the GTP_DUAL tile is reset; however, extra
clocking resources might be needed to generate the correct USRCLK frequency. In
Figure 6-8, a PLL is used to generate the TXUSRCLK and TXUSRCLK2 frequencies from
REFCLKOUT. A DCM can be used instead of the PLL, but the PLL is more convenient
when the REFCLKOUT rate is not an integer multiple of the required TXUSRCLK rates.
Figure 6-7: TXOUTCLK Drives Multiple GTP Transceivers with a 2-Byte Interface
GTP
Transceiver
PLLLKDET
TXOUTCLK LOCKED
TXUSRCLK2
TXUSRCLK
TXDATA (16 or 20 bits)
GTP
Transceiver
TXUSRCLK2
TXUSRCLK
TXUSRCLK
TXUSRCLK2
TXDATA (16 or 20 bits)
Selected
Divide-by-2
Solution
UG196_c6_07_040709
Design in
FPGA