I have a target board with only a few signals. I have created a very simple Blink LED project from the CubeMX software. It imports into Keil, compiles, and downloads to FLASH. But when it hits the debug window, it automatically executes crap. I can reset, stop, then single step. It says "Cannot access memory". I have the latest in Keil (5.23), unlocked with the M0+ license from ST. Also have the v1.19 of the CubeMX. I also downloaded ST Link Utility and Erased the memory manually. It goes back to default as I can see the memory real time. The only thing that I do not have are the 100k resistors on the SWD and CLK lines (recommended)
The ST Link Debugger was purchased from ST, so it is authentic. I have gotten a Nucleo board to work already, so I believe that Keil and the CubeMX are fine.
Uncheck "run to main()" and observe where the CPU is stopped
Make sure you have BOOT0 pulled low. Make sure the target voltage is wired to the ST-LINK.
>>I have a target board with only a few signals.
Not really providing much insight into the design.
Thanks for the help. I have another message from ST that states that the BOOT pin should be pulled low as well. I will try that.