Is there also an area(PROM) with microcode in the DSP?
Where a basic provision of the IC is made?
E.g. the query of BootMode and the subsequent forwarding to the system register?
Are you asking about booting(loading application code/data from PROM). If so, we recommend to refer POST example available in the below path:
C:\Program Files (x86)\Analog Devices\VisualDSP 5.1.2\Blackfin\Examples\ADSP-BF533 EZ-KIT Lite\Power_On_Self_Test
Refer Readme.txt which includes procedure to create and flashing the loader file.
Also, we recommend to refer EE-240(ADSP-BF533 Blackfin® Booting Process) www.analog.com/.../EE-240_Rev4.pdf
If this doesn't help, can you please explain your query in detail. Also let know know are you using custom board or Ezkit.