SystemClock_Config() fails with some clock rates

[iforce2d]

I'm trying a simple blinking LED on a STM32H743VIT6 with STM32CubeIDE 1.13.2, using the clock configuration wizard. When the clock rate is set to 90MHz everything is fine, but at 480MHz the program cannot get past the SystemClock_Config() call. 

When stepping through the code with a debug build, inside HAL_RCC_ClockConfig() this macro triggers the ST-Link to lose connection:

MODIFY_REG(RCC->CFGR, RCC_CFGR_SW, RCC_ClkInitStruct->SYSCLKSource);

When running a release build, the result is as if the SystemClock_Config() caused an endless loop.

Details: https://youtu.be/n0iYG4h2w8A

The clock source in the video is a 12MHz crystal but the same problem still occurs when not using it. I've never used a H7 before, maybe there's something I'm missing?

[TDK]

I'd guess a hardware issue. Either the current supply is insufficient at 480 MHz or something else about the power scheme isn't good. Can you power it via something else? Can you share the schematic?

[Pavel A. · Accepted solution]

This is a well known Cube issue for STM32H743/753. By default the chip version is "stepping Y", but most likely you have "stepping V", needed to unlock the 480 MHz clock. Select Stepping V in the RCC settings. Then follow the procedure described in the ref. manual.

[SofLit]

Hello,

If you have a Rev Y chip you cannot exceed 400MHz while with Rev V you can reach 480MHz.

So please check your chip revision.