NIOS is generating Read Signal Twice.

The misunderstanding is related to the fact that NIOS always performs 32bit read accesses, even if you explicitly use IORD_16DIRECT or IORD_8DIRECT: in these cases you'll always get multiple CS and RD strobes.

This can be annoying if your external address is a fifo or some register which is supposed to change at every read access.

The solution I used in a similar case is using a 32bit external data bus and connecting only the 8 or 16 bits I need; this way I always perform a single 32bit access and discard extra bits.