SBSFU with STM32F469/STM32F479 and SPI flash

[SL61]

Hi everyone,

I am using STM32F469/STM32F479 and want to integrate SBSFU with an SPI flash. Basically the active image is in MCU's 1 Mbytes flash and downloaded image is in the external flash. There are several questions I would like to know before I start.

• Refer to STM32F13ZHTx_FLASH.ld in STM32F413H_DISCOVERY_2_Images_SBSFU, there is a memory region for SE_CallGate. I assume this is a feature in firewall, which is not applied to F4 series. Do I need to care about it for my STM32F469?
• About memory region, can I simply change the address boundary in mapping_fwimg.ld and keep the same size for SBSFU itself for STM32F469? I just want to shrink the flash size for firmware image and keep SBSFU the same for simplicity.
• As for integrating the external flash for downloading new image, I plan to use the example in B-L475E-IOT01A as a reference. Is there any thing I need to aware in terms of the differences between F4 and L4 MCU?

Any suggestion is welcomed. Thanks.

Best,

Sean

[Bubbles]

Hello @SL61​ ,

1) The SE_CallGate is part of MPU isolation. It's basically an attempt to emulate firewall used on L4 by an MPU configuration. It's not a copy-paste error or some other unused stub.

2) when manipulating with memory mapping, you need to be careful about the MPU. MPU has some constraints and cannot be configured to protect any memory range.

3) The firewall is the biggest differentiator indeed. Also dual bank management is quite different on L4. Also H7 example features external flash, but I doubt it would be more helpful than L4.

BR

J.