Hi Asmita,
For supported DDR2 memory types refer to section 5.6.2.2 of the AM335X Datasheet Rev. F. U-boot code is included in the AM335X Linux EZSDK which can be downloaded from this link: http://software-dl.ti.com/sitara_linux/esd/AM335xSDK/latest/index_FDS.html
For DDR2 memory initialization please refer to this link: http://processors.wiki.ti.com/index.php/AM335x_EMIF_Configuration_tips