niosii + sdram connection problems

As you are using Nios II based system, you can use all the SOPC builder based components that are available with the SOPC Builder. I'm assuming that you are using CFI compliant flash memory. You can use the CFI Flash memory controller and SDRAM controller that are available with the SOPC Builder. To use CFI Flash memory controller (with Bi-directional IO), you'll need to use tri-state bridge component, which connects the bidirectional data bus with the avalon fabric's unidirectional data bus. The SDRAM controller can share this tri-state bridge or can be used independently. You need to use the tristate bridge for SDRAM only if the SDRAM shares the datapath with other tristate components on the board.