There are a lot of configuration registers that need to be set correctly to get this to work. Port muxes must be set to ALT5 or ALT6 as appropriate for the Flexbus pins FB_AD0 to FB_AD_15, FB_A0 to FB_A23, and FB control signals. You also need to configure the flexbus control pin functions so that you get a CS, WE, OE, BHE and BLE. The CSCR needs to be configured with a 16 bit port width and a suitable number of wait states.