Constraints When Implementing An External Rgmii; Figure 9-2: Timing Report Setup/Hold Illustration - Xilinx LogiCORE IP MAC v8.5 User Manual

Required Constraints
The implementation requires 7.554 ns of hold.
figure of -0.446 ns relative to the following rising edge of the clock (since the IDELAY has
acted to delay the clock by an entire period when measured from the input flip-flop). This
is less than the 0 ns required so there is slack.
GMII_RX_CLK
GMII_RXD[7:0],
GMII_RX_DV
GMII_RX_ER

Constraints when Implementing an External RGMII

The constraints defined in this section are implemented in the UCF for the example design
delivered with the core. Sections from this UCF are copied into the following descriptions
to provide examples. These examples should be studied in conjunction with the HDL
source code for the example design and with the description
GMII," on page
RGMII IOB Constraints
The following constraints target the flip-flops that are inferred in the top-level HDL file for
the example design. Constraints are set to ensure that these are placed in IOBs. The DDR
register constraints are not present for a Virtex-4 device or Virtex-5 device where DDR
components are instantiated rather than inferred.
1-Gigabit Ethernet MAC v8.5 User Guide
UG144 April 24, 2009
-- DISCONTINUED PRODUCT --
7.554 ns
8 ns

Figure 9-2: Timing Report Setup/Hold Illustration

61.
# RGMII Receiver Constraints: place DDR registers in IOB
INST "*rgmii_interface/rgmii_rxd_ddr*"
INST "*rgmii_interface/rgmii_rx_dv_ddr"
INST "*rgmii_interface/rgmii_rx_ctl_ddr" IOB = true;
# Inband Status Registers: place registers in IOB
INST "*rgmii_interface/link_status"
INST "*rgmii_interface/clock_speed*"
INST "*rgmii_interface/duplex_status" IOB = true;
www.xilinx.com
Figure 9-2 illustrates that this represents a
8 ns
-6.134 ns
t
SETUP
t
= 7.554 - 8
HOLD
= -0.446 ns
"Implementing External
IOB = true;
IOB = true;
IOB = true;
IOB = true;
R
= 8 - 6.134
= 1.866 ns
101