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Ethernet AVB Endpoint User Guide www.xilinx.com 103
UG492 July 23, 2010
Chapter 11
Constraining the Core
This chapter defines the Ethernet AVB Endpoint core constraints. An example user
constraints file (UCF) is provided for the core and the HDL example design.
Required Constraints
Device, Package, and Speedgrade Selection
The Ethernet AVB Endpoint core can be implemented in Spartan®-3, Spartan-3E, Spartan-
3A/3A DSP, Spartan-6, Virtex®-5 and Virtex-6 devices that are large enough to
accommodate the core, and meet the following speed grades:
• -1 for Virtex-5 and Virtex-6 devices
• -2 for Spartan-6 devices
• -4 for all Spartan-3 devices
I/O Location Constraints
No specific I/O location constraints are required.
Placement Constraints
No specific placement constraints are required.
Timing Constraints
The core can have up to five separate clock domains:
• plb_clk for the main EDK PLB and processor clock frequency
• host_clk for the management interface logic of the connected Tri-Mode Ethernet
MAC
• tx_clk for the MAC transmitter clock domain
• rx_clk for the MAC receiver clock domain
• rtc_clk for the“Real Time Clock” reference frequency
These clock nets and the signals within the core that cross these clock domains must be
constrained appropriately in a UCF.
Sections of UCF syntax are used in the following descriptions to provide examples.