Utilizing Memory Protection Unit on STM32?

Peter Lebbing peter at digitalbrains.com
Wed Feb 6 20:47:23 CET 2019

On 06/02/2019 18:54, Tom Li via Gnuk-users wrote:
> It's clear on the datasheet that the Cortex M3-series of microcontroller
> cores have an optional Memory Protection Unit (MPU), which is provided
> by both STM32 and GD32's chips.

Are you sure? The Cortex-M3 Programming Manual (PM0056) says:

> Refer to the corresponding device datasheet to see if the MPU is
> present in the STM32 type you are using.

If we now compare the datasheet for the STM32F103CB, the medium-density
device used in the GnuK, to an XL-density device like the STM32F103RFT,
I notice that the former has the following subsections of section 2.3:

| 2.3 Overview
| 2.3.1 ARM ® Cortex ® -M3 core with embedded Flash and SRAM
| 2.3.2 Embedded Flash memory
| 2.3.3 CRC (cyclic redundancy check) calculation unit
| 2.3.4 Embedded SRAM
| [...]

Whereas the latter, the XL-density part has:

| 2.3 Overview
| 2.3.1 ARM® Cortex®-M3 core with embedded Flash and SRAM
| 2.3.2 Memory protection
| 2.3.3 Embedded Flash memory
| 2.3.4 CRC (cyclic redundancy check) calculation unit
| 2.3.5 Embedded SRAM
| [...]

I must say, they could have presented this information in a much easier
way, but I think you're mistaken that the 103CB has an MPU. It's too

I also looked at the datasheet for a high-density device (in between the
103CB and the 103RFT), but it seemed to be missing the MPU as well.

I didn't check the GD32 part, but it would be quite a hefty upgrade if
they chose to include the MPU silicon on their version of the 103CB!



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