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Chapter 5: Using the Client-side GMII Data Path
Virtex-II Pro and Virtex-II Devices
Figure 5-14 illustrates how to create an external GMII transmitter in a Virtex-II family device. The signal names and logic shown on the figure exactly match those delivered with the example design.
Figure 5-14 shows that the input transmitter signals are registered in device IOBs before presenting them to the FPGA fabric. This logic achieves the required setup and hold times.
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| IOB LOGIC | Ethernet |
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gmii_tx_clk | IBUFG | BUFG | |
| gmii_tx_clk_ibufg | gmii_tx_clk_bufg | |
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IPAD |
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userclk2 (if RocketIO is used) gtx_clk (if TBI is used)
Transmitter
Elastic
Buffer
gmii_txd[0] | IBUF |
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| gmii_txd_ibuf[0] | gmii_txd_int[0] | |||||
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IPAD |
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| D Q |
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| gmii_txd[0] |
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gmii_tx_en | IBUF |
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| gmii_tx_en_ibuf |
| gmii_tx_en_int | ||
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IPAD |
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gmii_tx_en
gmii_tx_er | IBUF |
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| gmii_tx_er_ibuf |
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| gmii_tx_er_int | |
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IPAD |
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gmii_tx_er
Figure 5-14: GMII Transmitter Logic
62 | www.xilinx.com | Ethernet |
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| UG155 March 24, 2008 |