STM32H745 bootloader access after full chip flash erase

[GHolc.1]

I'm trying to verify my connection to the STM32H745 built in bootloader over UART 1, using pins PA9 and PA10 using STM32CubeProgrammer.  First I erased flash by using full chip erase flash memory in STM32CubeProgrammer using JLink/Flasher.  I then disconnect the JLink and change STM32CubeProgrammer to connect via UART, and power cycle.  Is my assumption correct that an erased flash on the H745 will automatically jump to the bootloader at power up?

The board is our own design, not a demo board, and is functioning as expected when our application code is loaded..  I have pin BOOT0 low.  I have a pull up on PB15.  I have flash erased.  STM32CubeProgrammer won't connect over UART.  When I have my application code in flash UART1 fully works, sending and receiving data so I can rule that out as a problem.  Anybody have suggestions what I might have wrong, or can confirm my assumption that a blank flash will jump to the bootloader on its own?

[TDK · Accepted solution]

> Is my assumption correct that an erased flash on the H745 will automatically jump to the bootloader at power up?

No, there is no empty flash check on the STM32H7.

STM32 microcontroller system memory boot mode - Application note

[GHolc.1]

I switched BOOT0 high and STM32CubeProgrammer immediately connects over UART so it seems like everything checks out and probably my jump to bootloader function call is the problem.