CM4 core clock limited to 64 MHz while CM7 runs at full configured frequency?

[Prathiksha]

I am working on the NUCLEO-H755ZI-Q, which contains a dual-core STM32H755 (Cortex-M7 + Cortex-M4).

I configure the system clocks in CubeMX as follows:

• SPI1/2/3 Clock MUX: 400 MHz
• System Clock: Configured for high-speed operation
• CM7 core frequency: Correctly matches the configured value (e.g., 200 MHz / 400 MHz depending on settings)

However, when I debug or read the CM4 core clock, I always see:

• CM4 clock = 64 MHz
• It does NOT increase even when I configure higher values in CubeMX. 

Regards,

Prathiksha

[AScha.3]

How you "see" the 64Mhz ?

 

[TDK]

It's probably an issue with how you're running the program. If the CM7 core is doing the clock configuration, it needs to do that before the clock will be updated. Just running the CM4 side will use the default clock (64 MHz).

[mƎALLEm]

---

@Prathiksha wrote:

However, when I debug or read the CM4 core clock, I always see:

• CM4 clock = 64 MHz

---

How did you check that?

[mƎALLEm]

Hello and thank you for the sharing. I don't see where do you get the CM4 in the attached firmware. Could you please clarify?

 

[mƎALLEm]

Hello,

You've previously shared that project but my question was: 

So please clarify how you measured the clock frequencies in the firmware attached.

 

[TDK]

Keep in mind what you are claiming is impossible. The CM7 and CM4 clocks are not independent. It is not possible for the CM7 to be at 200/400 MHz while the CM4 is only at 64 MHz. So there has to be an error in how you're measuring, or how you're interpreting something.