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Chapter 6: The Ten-Bit Interface
IOB LOGIC |
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IBUFG | gtx_clk_ibufg | BUFG | |
gtx_clk |
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IPAD | (125 MHz) |
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component_name_block (Block Level from example design)
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| IOB LOGIC |
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Ethernet |
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or SGMII LogiCORE |
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'0' | D | Q |
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gtx_clk |
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| pma_tx_clk_obuf |
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| OPAD | |
'1' | D | Q |
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| OBUF | |
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tx_code_group[0] |
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tx_code_group[9] | tx_code_group_int[9] |
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Figure 6-1: Ten-Bit Interface Transmitter Logic
Receiver Logic
Virtex-II and Virtex-II Pro Devices
Figure 6-2 illustrates an external receiver TBI in Virtex-II devices. The signal names and logic displayed precisely match those delivered with the example design when the TBI is chosen.
Figure 6-2 shows that the input receiver signals are registered in device IOB Double-Data Rate (DDR) input registers, alternatively on the rising edges of both pma_rx_clk0_bufg and pma_rx_clk1_bufg (pma_rx_clk0 and pma_rx_clk1 are 180 degrees out of phase with each other). This splits the input TBI data bus, rx_code_group[9:0], up into two buses: rx_code_group0_reg[9:0] and rx_code_group1_reg[9:0],
70 | www.xilinx.com | Ethernet |
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| UG155 March 24, 2008 |