Write your own AVALON storage control cannot be identified in the NIOS II into memory

Myself with Verilog language block an external storage controller control EEPROM (can read \ write infinite times).But could not put the address in the NIOS II when the storage space to use, in writing, please what is the law when the IP?Use _SWTIO_ instruction can be read and write properly this period of memory space, means that the timing is right, IP core is conform to the AVALON bus specification.But, I hope this space will be NIOS had normal memory usage, rather than a peripheral registers