STM32H7 connect but Can't program without NRST connection.

[Rob Ashworth]

I am having a strange (to me) issues trying to program an STM32H743VI.

I have had the PCB manufactured and assembled by a different supplier and all of a sudden I cannot program the STM32H743....

I do not have the NRST pin back to the STLink-V2, only the SWDIO pins, GND and 3V3.

It's as if it is not booting correctly, but not quite sure where to look to see what is happening, or what could have changed!  Certainly the design is identical, only the supplier is different.

I have verified the 100nF cap on NRST, and the 10K resistor on BOOT0.  Both OK.

[TDK]

It says target voltage is 0.5 V. That is insufficient for operation. That means the programmer thinks the VCC line is at 0.5 V.

Verify voltage rails are okay and VCAP voltages are okay using a multimeter.

[MHoll.2]

On Your schematics You have PDR_ON at GND, according to the Datasheet if PDR_ON is on GND You need to use an external voltage supervisor. Do You realy need to have the chip running down to 1.62V?

[Rob Ashworth]

I don't think it is a Power supply issue - This is fixed at 3V3, and I have the same PDR_ON configuration on many other boards without issue.  the ST-link connects, and sometimes I can blank 1 sector of memory, but after that it fails to communicate. Getting a bit stuck here.

[Rob Ashworth]

Issue sorted.  The supplier had not reflowed the ARM controller properly.