STM32 Peripheral lock (STM32h755)

[sarun]

I am working on an  application where I plan to relocate all non-safety modules to the CM4 core. To achieve full safety, I need a mechanism to lock the peripherals so that the CM4 core cannot access any peripherals configured in the CM7 core, including multiple instances of SPI, UART, I2C, CAN, and GPIO (on register level).

As per the reference manual, I did not find a mechanism to lockout specific cores.

One alternative I tried is using the Memory Protection Unit (MPU). However, my investigation revealed that the CM4 MPU can lock CM4 from accessing only 6 regions. Given that we have more than 6 regions, configuring the MPU seems insufficient based on our requirements. 

Can it be done with MPU or Is there any alternatives for this ?

[SofLit · Accepted solution]

Hello,

I don't think there is an alternative for this kind of protection for STM32h755 except using MPU.

Meanwhile, see if IEC61508-compliant safety concept for H7 dual core included in Safety manual UM2840 can help you (I'm not expert of security subjects).

[sarun]

Hi @SofLit,

Thank you for your response. I have been doing some further investigation but, unfortunately, came up empty-handed. Due to the limited number of CM4 MPU regions (8), seems like there are no alternatives.

The methods mentioned in the safety manual (Peripheral lock) dosent provide access restriction to all registers.

[SofLit]

Unfortunately, I think there are no other alternatives than using MPU and what I've provided to you.