How to acess external peripherals with nios ,which share common pins of fpga

Hai,

In my development board i want to access the ADC and DAC from the fpga.The DAC and ADC share the common pins of the FPGA.I have found out that i can use the tristate controller module for use in Qsys to access the shared pins.But i am not getting any idea on how to use it for custiomed components like ADC and DAC.Can anyone help me?