Xilinx LOGICORE UG144 - Manual (Page 99)

1-Gigabit Ethernet MAC v8.5 User Guide www.xilinx.com 99
UG144 April 24, 2009
Required Constraints R
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Understanding Timing Reports for GMII Setup/Hold Timing
Non-Virtex-5 devices
Setup and Hold results for the GMII input bus can be found in the data sheet section of the
Timing Report. The results are self-explanatory and it is easy to see how they relate to
Figure 9-1 . Following is an example for the GMII report from a Virtex-4 device. The
implementation requires 1.531 ns of setup—this is less than the 2 ns required so there is
some slack. The implementation requires -0.125 ns of hold— this is less than the 0 ns
required so there is some slack.
Data Sheet report:
-----------------
All values displayed in nanoseconds (ns)
Setup/Hold to clock gmii_rx_clk
------------+------------+------------+------------------+--------+
| Setup to | Hold to | | Clock |
Source | clk (edge) | clk (edge) |Internal Clock(s) | Phase |
------------+------------+------------+------------------+--------+
gmii_rx_dv | 1.531(R)| -0.141(R)|gmii_rx_clk_bufg | 0.000|
gmii_rx_er | 1.531(R)| -0.141(R)|gmii_rx_clk_bufg | 0.000|
gmii_rxd<0> | 1.531(R)| -0.141(R)|gmii_rx_clk_bufg | 0.000|
gmii_rxd<1> | 1.525(R)| -0.135(R)|gmii_rx_clk_bufg | 0.000|
gmii_rxd<2> | 1.531(R)| -0.141(R)|gmii_rx_clk_bufg | 0.000|
gmii_rxd<3> | 1.525(R)| -0.135(R)|gmii_rx_clk_bufg | 0.000|
gmii_rxd<4> | 1.515(R)| -0.125(R)|gmii_rx_clk_bufg | 0.000|
gmii_rxd<5> | 1.515(R)| -0.125(R)|gmii_rx_clk_bufg | 0.000|
gmii_rxd<6> | 1.520(R)| -0.130(R)|gmii_rx_clk_bufg | 0.000|
gmii_rxd<7> | 1.520(R)| -0.130(R)|gmii_rx_clk_bufg | 0.000|
------------+------------+------------+------------------+--------+
Virtex-5 devices with Delayed Data/Control
Setup and Hold results for the GMII input bus can be found in the data sheet section of the
Timing Report. The results are self-explanatory and it is easy to see how they relate to
Figure 9-1 . Here follows an example for the GMII report from a Virtex-5 device. The
implementation requires 1.962 ns of setup—this is less than the 2 ns required, so there is
slack. The implementation requires –0.008 ns of hold—this is less than the 0 ns required, so
there is slack.