Required Constraints

R

The following UCF syntax shows these constraints being applied.

#***********************************************************

# PCS/PMA Clock period Constraints: please do not relax * #***********************************************************

NET "userclk2" TNM_NET = "userclk2";

TIMESPEC "TS_userclk2" = PERIOD "userclk2" 8 ns HIGH 50 %;

NET "dclk" TNM_NET = "dclk";

TIMESPEC "TS_dclk" = PERIOD "dclk" 20 ns HIGH 50 %;

Setting MGT Transceiver Attributes

The Virtex-4 MGT device has many attributes. These attributes are set directly from HDL source code for the transceiver wrapper file delivered with the example design. These are in the file transceiver.vhd (for VHDL design entry) or transciever.v (for Verilog design entry). See the Ethernet 1000BASE-X PCS/PMA or SGMII Getting Started Guide for a detailed description of the example design provided with the core.

This HDL transceiver wrapper file was initially created using Architecture Wizard. See the Virtex-4 FPGA RocketIO Multi-Gigabit Transceiver User Guide (UG076) for a description of available attributes.

MGT Placement Constraints

The following UCF syntax illustrates the MGT placement contraints for the example design. Because Virtex-4 MGTs are always available in pairs, two MGTs are always instantiated in the example design, even if one is inactive.

#***********************************************************

# Example Rocket I/O placement* #***********************************************************

# Lock down the REFCLK pins:

NET

brefclk_p

LOC

=

F26;

NET

brefclk_n

LOC

=

G26;

# Lock down the GT11 pair and GT11 clock module

INST "core_wrapper/rocketio/GT11_1000X_A" LOC = GT11_X0Y5; INST "core_wrapper/rocketio/GT11_1000X_B" LOC = GT11_X0Y4; INST "GT11CLK_MGT_INST" LOC = GT11CLK_X0Y3;

#Lock down the RocketIO pins: NET "rxp0" LOC = J26;

NET "rxn0" LOC = K26; NET "txp0" LOC = M26; NET "txn0" LOC = N26; NET "rxp1" LOC = U26; NET "rxn1" LOC = V26; NET "txp1" LOC = P26; NET "txn1" LOC = R26;

Ethernet 1000BASE-X PCS/PMA or SGMII v9.1

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UG155 March 24, 2008

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Xilinx 1000BASE-X manual Setting MGT Transceiver Attributes, MGT Placement Constraints