application jump to system memory bootloader

Hi,

I have an stm32l43 connected as a USB device. Using the BOOT0 pin, I can start the built-in Bootloader and use DFU. Now I wish to jump to the BL without this Pin by a software jump.

But with this jump, I only seem to reset the device (my code starts again like after a reset). It seems to me that the Bootloader starts, checks for valid code in flash and then streight jumps back there (as my firmware of course is valid code).

How can I get the Bootloader staying active without using a boot pin or an option bit?

here is my jump function for reference:

void jump2STinternalBootloader(void){
	void (*SysMemBootJump)(void);
 
	/**
	 * Set system memory address.
	 * check AN2606 document for descriptions of memory addresses
	 */
	volatile uint32_t addr = 0x1FFF0000;
 
	/**
	 * Disable RCC, set it to default (after reset) settings
	 * Internal clock, no PLL, etc.
	 */
	HAL_RCC_DeInit();
 
	/**
	 * Disable systick timer and reset it to default values
	 */
	SysTick->CTRL = 0;
	SysTick->LOAD = 0;
	SysTick->VAL = 0;
 
	/**
	 * Disable all interrupts
	 */
	__disable_irq();
 
	/**
	 * Remap system memory to address 0x0000 0000 in address space
	 */
	__HAL_SYSCFG_REMAPMEMORY_SYSTEMFLASH();
 
	/**
	 * Set jump memory location for system memory
	 * Use address with 4 bytes offset which specifies jump location where program starts
	 */
	SysMemBootJump = (void (*)(void)) (*((uint32_t *)(addr + 4)));
 
	/**
	 * Set main stack pointer.
	 * This step must be done last otherwise local variables in this function
	 * don't have proper value since stack pointer is located on different position
	 *
	 * Set direct address location which specifies stack pointer in SRAM location
	 */
	__set_MSP(*(uint32_t *)addr);
 
	/**
	 * Actually call our function to jump to set location
	 * This will start system memory execution
	 */
	SysMemBootJump();
	while(1);
}