Hi, Semikim,
Regarding your question, I suggest you refer to the an4759.pdf located at the link:
https://www.nxp.com/docs/en/application-note/AN4759.pdf
The bootloader code is put at the top of program flash, located at from 0x1F400 to 0x1FFFF, after Reset, the DSC jump to the bootloader code, it monitor the SCI port, if it can not detect the SCI character until DelayTime, it will jump to application code, the application code Start Address is put at the address 0x1F3FD.
Hope it can help you
BR
Xiangjun Rong