About the LPC435X memory address, please refer to the user manual section 3.3 "MDK Configuration and Compilation".

Moreover, please erase the program of the internal flash before downloading program to SPI flash and confirm the SW2 position referring to section 2.4.2 "BOOT Setting".

When you use ULINK2 to download program, please pay attention to the Notes mentioned in section 3.4.2 "Download Program by ULINK2".