Setting The Clocking Options; Figure 2-10: Dcm Clocking - Xilinx Virtex-4 RocketIO User Manual

R
Reference
Clock

Setting the Clocking Options

Because of the MGT's flexibility, there are many different clocking modes available. The
RocketIO wizard can automatically configure the MGT clocking options for any rate
supported by the device.
Note:
frequencies to clock data, it is recommended to use TXOUTCLK1 and RXRECCLK1 in conjunction
with the internal clock dividers.
Virtex-4 RocketIO MGT User Guide
UG076 (v4.1) November 2, 2008
User DATA
CLKIN
DCM
Note: Only DCM outputs CLK0
and DV are suitable; the FX
output is not supported
.
User DATA

Figure 2-10: DCM Clocking

The reference clock can directly drive the USRCLKs. Because most cases require multiple
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Setting the Clocking Options
REFCLK1
TXOUTCLK1
TXDATA
TXCHARDISPMODE
TXCHARDISPVAL
TXCHARISK
Etc.
GT11
Interface
Width
TXUSRCLK2
1 Byte
RXUSRCLK2
2 Byte
TXUSRCLK
4 Byte
RXUSRCLK
8 Byte
RXDATA
RXCHARISCOMMA
RXRUNDISP
RXCHARISK
Etc.
Note: DCM is not needed
for the 4-byte mode.
RXRECCLK1
USRCLK2 to
USRCLK Ratio
4:1
2:1
1:1
1:2
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