Xilinx Spartan-3A User Manual

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Contents

126 www.xilinx.com Spartan-3A/3AN Starter Kit Board User GuideUG334 (v1.0) May 28, 2007Chapter 15: Expansion Connectors RDifferential I/O ConnectorsThe Spartan-3A/3AN Starter Kit board includes stake pin headers with excellent signalintegrity and matched impedance traces to demonstrate high-performance differentialI/O. Each differential pair supports approximately 600 Mbits per second (Mbps) datarates. All I/O pairs support differential input termination (DIFF_TERM) as described inthe Spartan-3A and Spartan-3AN data sheets.The board is primarily designed to support loopback operations using a standard 34-pinsocket-to-socket cable.The two differential I/O headers, shown in Figure 15-1, page 121, consist of a 2x17 array ofstake pins arrange on 0.1-inch centers. The headers are not keyed. Ground pins areinterspersed with the signal pins for improved signal integrity over any attached cable.Power is also supplied, via the nominally 3.3V rail, labeled VCCO_012. The powerconnectors are for potential daughter cards that plug into the connector.The J15 connector is primarily designed to transmit output data while the J2 connector isprimarily designed to receive input data. However, both headers are equally good attransmitting differential data. The “Receive” header does have special provisions forcapturing the receive clock input.The pin assignment for the J2 “Receive” connector appears in Table 15-2 and in Table 15-4.The FPGA ball assignment is listed in parentheses.The pin assignment for the J15 “Transmit” connector appears in Table 15-3 and inTable 15-4. The FPGA ball assignment is listed in parentheses.Table 15-2: Receive” Header (J2)2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34GND GND RXN_0(B4) GND RXN_1(A5) GND RXN_2(A6) 3.3V 3.3V 3.3V RXN_3(A8) GND RXN_4(C10) GND RX_CLK_N(A11)GND GNDGND GND RXP_0(A4) GND RXP_1(B6) GND RXP_2(A7) 3.3V 3.3V 3.3V RXP_3(A9) GND RXP_4(A10) GND RX_CLK_P(A12)GND GND1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33Table 15-3: Transmit” Header (J15)2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34GND GND TXN_0(AA3) GND TXN_1(AA4) GND TXN_2(AB6) 3.3V 3.3V 3.3V TXN_3(AB7) GND TXN_4(AB8) GND TX_CLK_N(AB10)GND GNDGND GND TXP_0(AB2) GND TXP_1(AB3) GND TXP_2(AA6) 3.3V 3.3V 3.3V TXP_3(Y7) GND TXP_4(AA8) GND TX_CLK_P(AA10)GND GND1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33