Using the SDRAM, the distributed loading file is used, and the Hardfault_handler appears.

After using SDRAM, SDRAM may be used as a data area. If the SDRAM is partitioned into a data area, it must be initialized before calling the main function if the file is distributed in a decentralized manner. Otherwise, Hardfault_handler will appear. Because the address in the SDRAM is used, and the SDRAM is not initialized at this time, the address is out of bounds. can be initialized in the startup code:
Reset_handler PROC
EXPORT Reset_handler [WEAK]
IMPORT Systeminit
IMPORT __low_level_init
IMPORT __main
LDR R0, =systeminit
BLX R0
LDR R0, =__low_level_init
BLX R0
LDR R0, =__main
BX R0
Endp

In __low_level_init, call Emc_init () to initialize the SDRAM.