TMDXEVM5515: Is the SDRAM on board necessary?

Part Number:TMDXEVM5515

Hi,

we found there is a SDRAM 8MByte on board. When we make our board, we need to confirm whether it is necssary? in other word, whether the main code stored in flash would be loaded into it to execute or in an RAM inside 5515?

another issue is when I tried to disable it by pulling up the signal of SD_CEXn, I can't find the register to do it. There is no related register description in 5515 datasheet. Please help.