Ethernet 1000BASE-X PCS/PMA or SGMII v9.1
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UG155 March 24, 2008
Clock Sharing Across Multiple Cores with RocketIO
R
Clock Sharing Across Multiple Cores with RocketIO
Virtex-II Pro Devices
Figure 7-5
illustrates sharing clock resources across two instantiations of the core on the
same half of the device when using the core with the Virtex-II Pro MGT. Note that more can
be added by instantiating the cores using the block level (from the example design) and
continuing to share
userclk
,
userclk2
, and
brefclk
across all instantiations. For each
core,
userclk
and
userclk2
must always be derived from the
brefclk
or
refclk
used
by that core.
When using the fixed routing resources of
brefclk
, MGTs along the top edge of the
device must use a separate
brefclk
routing resource to those along the bottom edge of
the device. For more information, see the
Virtex-II Pro RocketIO Transceiver User Guide
(UG024). Each
brefclk
domain must use its own DCM to derive its version of
userclk
and
userclk2
.
Figure 7-5:
Clock Management: Two Core Instances, Virtex-II Pro
MGTs for 1000BASE-X
DCM
CLKIN
CLK0
CLK2X180
FB
BUFG
BUFG
IBUFGDS
TXUSRCLK
BREFCLK
TXUSRCLK2
RXUSRCLK
RXUSRCLK2
GT_ETHERNET_1
brefclk (62.5MHz)
userclk (62.5 MHz)
userclk2 (125 MHz)
Ethernet 1000BASE-X
PCS/PMA or
SGMII core
Customer Design
userclk
userclk2
TXUSRCLK
BREFCLK
TXUSRCLK2
RXUSRCLK
RXUSRCLK2
GT_ETHERNET_1
Ethernet 1000BASE-X
PCS/PMA or
SGMII core
userclk
userclk2
IPAD
brefclkp
IPAD
brefclkn
component_name_block
(Block Level)
component_name_block
(Block Level)