How to hold STM32H745 in reset and still connect with JTAG debugger

[DKrzm.1]

I would like to hold the STM32H745 in reset and then connect with JTAG and be able to reprogram the flash internally. I am finding that their is some setting that is damaging a part on boot up and want to prevent the device from booting but still be able to use JTAG to reprogram the internal flash. I have tried holding the NRST pin low but I am unable to connect with JTAG then. Thanks.

[Uwe Bonnes]

Connect under reset?

[DKrzm.1]

Correct, such that I can reprogram the flash without it starting to boot.

[Uwe Bonnes]

That may be a chicken egg problem. As soon as you power your board, it will run. If you connect the debugger and start the debugger with the target unpoweered, debugger will not find the target and not keep the board under reset. So probably manual holding the board under reset until the debugger takes over the reset is another option.