STM32H7 single core, which RAM is good for code?

[Pavel A.]

Dear experts,

A customer asks me to copy application from flash to RAM and run in RAM.

Not sure if this is justified. If I remember correctly it is not so much on 'F4, but maybe on H7 RAM performs much better? Anyway they pay for this so...

I've created a project in latest Atollic and selected Target settings-> Code location = RAM.

It generates linker script where both code and data goes to DTCRAM at 0x20000000.

From description of the memory layout in the H7 RM DTCM RAM area is not suitable for code:

"The DTCM-RAM can be used as read-write segment to host critical real-time data (such as

stack and heap) for application running on Cortex®-M7 CPU".

But it seems to work, with cache disabled.

I tried to change the link script: ITCM RAM for code and DTCM for data. This of course works.

So, is DTCRAM good for code or it works by coincidence and not supported officially?

Where I can find better explanation of the RAM parts of H753/743?

Thanks,

-- Pavel A.

[Tesla DeLorean · Accepted solution]

Some technical material on the CM7 might be of most help.

The ITCM​ would have connectivity to the I-bus. The TCM is not cached as it already has speed and proximity working for it. The multiple buses allow for Harvard operation with them.

The FLASH should be reasonably comparable, given the ART and architectural cache.

Would recommend benchmarking code execution in different memories.​

[waclawek.jan]

JW

[Pavel A.]

Thank you gentlemen.

Back to reading the f* manuals instead of productive work ... the customer wants to show off and use H7 (new to me) - though F4 just enough for their project.

-- pa

[waclawek.jan]

> customer wants to show off and use H7 ... though F4 just enough for their project.

That is very unreasonable.

JW