94 www.xilinx.com Spartan-3A/3AN Starter Kit Board User GuideUG334 (v1.0) May 28, 2007Chapter 12: SPI Serial Flash RShared SPI Flash and Platform Flash Data LineThe SPI_MISO signal from the two SPI Flash PROMs is shared with data output signalsfrom the parallel NOR Flash PROM and the serial output from the Platform Flash PROMas shown in Table 12-3. To avoid contention, the FPGA application must ensure that onlyone data source is active at any time.Jumper Settings to Configure FPGA from Selected SPI Flash PROMTo successfully configure the FPGA from the selected external SPI Flash PROM, set thefollowing jumpers as described below.• Set the FPGA configure mode, using the Jumper J26 jumper header, shown inTable 12-4.• Disable the Platform Flash PROM using Jumper J46, shown in Table 12-4.• Select one of the SPI serial Flash PROMs as the SPI configuration source, as shown inTable 12-2.Table 12-3: Possible Potential Competing Devices on SPI_MISO (NF_D<0>) DataSignal orJumper Disabled Device Disable ValueJumper J46FPGA_INIT_BPlatform Flash PROM. Set to “Disabled” or “Enableduring Configuration” asshown in Table 4-2, page 40.FPGA_INIT_B has no effect.If set to “Always Enabled,” thenFPGA_INIT_B must be 1SPI_SS_B SPI Flash PROM selected byJumper J1, as shown inTable 12-2, page 93.1ALT_SS_B SPI Flash PROM selected byJumper J1, as shown inTable 12-2, page 93.1NF_CENF_OEParallel Flash PROM NF_CE = 1 or NF_OE = 1Table 12-4: Configuration Mode Jumper Settings for Master SPI Mode (J26, J46)Configuration ModeMode PinsM2:M1:M0 Jumper J26 SettingsPlatform FlashEnable (J46)Master SPI 0:0:1M0M1M2J26DONECEGNDJ46PROM
