DBGMCU internal peripheral

1 Article purpose[edit]

The purpose of this article is to:

  • briefly introduce the DBGMCU peripheral and its main features
  • indicate the level of security supported by this hardware block
  • explain how each instance can be allocated to the three runtime contexts and linked to the corresponding software components
  • explain, when necessary, how to configure the DBGMCU peripheral.

2 Peripheral overview[edit]

The DBGMCU peripheral is used to configure internal peripherals behavior when one of the cores (Cortex®-A7 or Cortex®-M4) enters in debug mode.
For instance, it allows to freeze a watchdog (IWDG) to avoid getting a watchdog reset when the Cortex®-A7 enters in debug mode (via a breakpoint or JTAG break).

2.1 Features[edit]

Refer to the STM32MP15 reference manuals for the complete list of features, and to the software components, introduced below, to see which features are implemented.

2.2 Security support[edit]

The DBGMCU is a non secure peripheral.

3 Peripheral usage and associated software[edit]

3.1 Boot time[edit]

DBGMCU is partly initialized by the FSBL at boot time in order to freeze IWDG2 when the Cortex®-A7 enters in debug mode.

3.2 Runtime[edit]

3.2.1 Overview[edit]

There is no real runtime support for DBGMCU. Instead, users who need to freeze some peripherals for a debug session should complete the minimal initialization done in the FSBL with their needs.

3.2.2 Software frameworks[edit]

Domain Peripheral Software frameworks Comment
Cortex-A7
secure
(OP-TEE)
Cortex-A7
non-secure
(Linux)
Cortex-M4

(STM32Cube)
Trace & Debug DBGMCU

3.2.3 Peripheral configuration[edit]

The configuration is applied by the firmware running in the context to which the peripheral is assigned. The configuration can be done alone via the STM32CubeMX tool for all internal peripherals, and then manually completed (particularly for external peripherals), according to the information given in the corresponding software framework article.

3.2.4 Peripheral assignment[edit]

Internal peripherals

Check boxes illustrate the possible peripheral allocations supported by STM32 MPU Embedded Software:

  • means that the peripheral can be assigned () to the given runtime context.
  • is used for system peripherals that cannot be unchecked because they are statically connected in the device.

Refer to How to assign an internal peripheral to a runtime context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possiblities might be described in STM32MP15 reference manuals.

Domain Peripheral Runtime allocation Comment
Instance Cortex-A7
secure
(OP-TEE)
Cortex-A7
non-secure
(Linux)
Cortex-M4

(STM32Cube)
Trace & Debug DBGMCU DBGMCU No assignment




debug and test protocol, named from the Joint Test Action Group that developed it

Open Portable Trusted Execution Environment

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