1. DDR SDRAM Data Initialization (DDR_DATA_INIT)
this is the value that will be written to the DDR2 after initialization has completed if D_INIT bit is set before MEM_EN is set. the value in this register is not very important, it is to initialize the DRAM DDR2 mostly useful when ECC is enabled.
2. DDR Initialization Address (DDR_INIT_ADDR)
3. DDR Initialization Enable Extended Address (DDR_INIT_EXT_ADDR)
the above two registers is most of time is left at zero. this is the starting address of 128 byte, that will be used by the controller to perform the DDR initialization