STM ROM Bootloader issue with STM32H745

[HKapo.1]

Hello,

I am facing a weird issue with accessing STM ROM bootloader for flashing.

Hardware Used: STM32H745-DISCO

IDE: Keil

I have created a simple bootloader which jumps to ROM Bootloader at startup.

startup_stm32h745xx.s:

; Reset handler
Reset_Handler PROC
 EXPORT Reset_Handler [WEAK]
				;Then check if we need to jump to ST Boot loader
 LDR R1, =0xE000ED00 ; SCB
 LDR R0, =0x1FF09800 ; ROM BASE
 STR R0, [R1, #8] ; VTOR
 LDR SP,[R0, #0] ; ROM Stack Pointer
 LDR R0,[R0, #4] ; ROM Program Counter
 BX R0	

When I power cycle and try to connect via STM32 CubeProgrammer, I get below error:

 

But when I press Reset button on STM32H745-DISCO, then connection is succesful without any issue

 

I am wondering what's the difference between pressing reset button and power cycle.

Any advice on how I can fix the issue.

[Tesla DeLorean]

You get one shot out of reset, any noise on any of the watched pins will be taken as a connection attempt. Probably more pins moving as it powers up.​

[HKapo.1]

The STM ROM bootloader present is V9.0 and seems there is a know bug with it

 

"– Additional reset needed after power off/on to enable connection to the BL interfaces"

Is there any workaround for this?

[Tesla DeLorean]

>>Is there any workaround for this?

Field programming, probably don't use the system's boot loader, but rather your own, using some protocol supported by standard/common tools?