Passing a bidirectional bus through an FPGA without knowing the bus protocol won't work.
While FPGA I/O pins do support tristate logic signals (floating output state), you will need to know when to drive a value onto the output, and when to tristate the output (high impedence, or 'Z').
Once you have a signal (for example out_enable
) that is '1' when you want to drive a value and '0' when the output should be floating, you can use a tri-state buffer to drive the output:
out_pin <= out_signal when(out_enable='1') else 'Z';