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Zainulabedeen
Associate III
June 10, 2026
Solved

Halting the FDCAN peripheral during debugging break points.

On STM32H733, the HAL provides __HAL_DBGMCU_FREEZE_FDCAN() in stm32h7xx_hal.h but it is conditionally compiled:

#if defined(DBGMCU_APB1HFZ1_DBG_FDCAN)
#define __HAL_DBGMCU_FREEZE_FDCAN() (DBGMCU->APB1HFZ1 |= (DBGMCU_APB1HFZ1_DBG_FDCAN))
#endif

DBGMCU_APB1HFZ1_DBG_FDCAN is not defined in stm32h733xx.h, so the macro does not exist at compile time and calling it gives:

error: implicit declaration of function '__HAL_DBGMCU_FREEZE_FDCAN'

Questions:

  1. Is FDCAN freeze during debug halt supported on STM32H733?
  2. If yes, why is DBGMCU_APB1HFZ1_DBG_FDCAN missing from stm32h733xx.h — is this a bug in the device header?
  3. What is the correct bit position to use as a workaround via direct register write?

 

I need to pause the FDCAN peripheral during debugging, that is my goal.

 

Thanks you very much for helping me out.

 

mƎALLEm
mƎALLEmBest answer
ST Technical Moderator
September 30, 2026

Hello ​@Zainulabedeen and sorry for the late reply.

Some stuff need to take time to follow-up and check in deep from our side.

The DBGMCU bit is no longer used for FDCAN freeze, so APB1HFZ1 should be removed from the documentation. In fact it has no effect on the FDCAN behavior.

From other hand, in debug mode, the set/reset on read feature is automatically disabled during the debugger register access and enabled during normal MCU operation. This information will be added in the documentation.

Hope I’ve answered your question.

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4 replies

mƎALLEm
ST Technical Moderator
June 10, 2026

 

Hello,

I’m analyzing this. I’ll get back to you.

In fact for STM32H743 (RM0433) I’m seeing, the register has been removed from the RM :

It was available in an old version of RM0433:

while it’s available in the HAL :

stm32h7xx_hal.h:

stm32h743xx.h: 

I will check internally and I’ll get back to you.

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Zainulabedeen
Associate III
June 16, 2026

​@mƎALLEm 

Following up, Kindly let me know what i can do.

mƎALLEm
ST Technical Moderator
June 16, 2026

Please kindly be patient. I don’t have the information yet. If I have one I will share it with you.

Thank you for your understanding.

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