Why is my TouchGFX project working despite exceeding the MCU's flash size?

wow · ‎2025-02-11

Hello,

I initially implemented TouchGFX on an Nucleo board with an STM32G071RBT6 (128K flash).

Currently, I am using a custom PCB with an STM32G071R8T6 (64K flash), but I did not change the MCU model in STM32CubeIDE.

However, despite the build analyzer showing a flash usage of 90K, the application appears to be running normally.

The images are stored in SPI flash, but I expected the application to fail due to exceeding the MCU’s 64K flash limit.

What could be the reason why the application is still functioning seemingly without issues?

I have attached an image showing the memory usage in the build analyzer.

Thank you!

Peter BENSCH · ‎2025-02-11

Your STM32G071R8T6 probably contains a so-called umbrella device, i.e. a chip with more flash, but which has only been partially tested and for which only the parameters from the data sheet are guaranteed. So if your STM32G071R8T6 happens to work anyway, there is no guarantee that it will work under all conceivable circumstances (VCC range, temperature range, frequency range, etc.).

You can therefore use this flash, which has been tested for 64KB, for more than 128KB when debugging, but you shouldn't be surprised if something doesn't work the way you want it to. Under no circumstances should you use this in production, however, because the function not mentioned in the data sheet is neither tested nor guaranteed, and later chip revisions may actually physically contain the smaller flash.

Does it answer your question?

Regards
/Peter

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View solution in original post

Peter BENSCH · ‎2025-02-11

Your STM32G071R8T6 probably contains a so-called umbrella device, i.e. a chip with more flash, but which has only been partially tested and for which only the parameters from the data sheet are guaranteed. So if your STM32G071R8T6 happens to work anyway, there is no guarantee that it will work under all conceivable circumstances (VCC range, temperature range, frequency range, etc.).

You can therefore use this flash, which has been tested for 64KB, for more than 128KB when debugging, but you shouldn't be surprised if something doesn't work the way you want it to. Under no circumstances should you use this in production, however, because the function not mentioned in the data sheet is neither tested nor guaranteed, and later chip revisions may actually physically contain the smaller flash.

Does it answer your question?

Regards
/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.