96
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
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
, 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
Transcei
v
er
PLLLKDET
TXOUTCLK
LOCKED
TXUSRCLK2
TXUSRCLK
TXDATA (16 or 20
b
its)
GTP
Transcei
v
er
TXUSRCLK2
TXUSRCLK
TXUSRCLK
TXUSRCLK2
TXDATA (16 or 20
b
its)
Selected
Di
v
ide-
b
y-2
Sol
u
tion
UG196_c6_07_040709
Design in
FPGA