External RAM base address configuration for TouchGFX on STM32N657X0H3Q1

[siddum]

Dear ST Support Team,

We are currently working with the STM32N657X0H3Q1 controller and configuring TouchGFX to use an external RAM device.

The external memory used in our design is S80KS5123GABHB020 (512 MB Octal RAM) connected via XSPI. The external RAM is intended to be used for TouchGFX frame buffers and graphics-related data.

While configuring TouchGFX with the external memory in STM32CubeMX / application code, we need to set the base address of the external RAM. However, we would like clarification on the following point:

• What is the correct memory-mapped base address that should be configured for the external RAM (S80KS5123GABHB020) when used with the STM32N657X0H3Q1 for TouchGFX ?

• Is this address fixed by the STM32N6 memory map, or does it depend on the XSPI instance and configuration (XSPI1 / XSPI2)?

• Are there any specific recommendations or constraints for using this external RAM as TouchGFX frame buffer memory?

Your guidance on the correct address configuration and any best practices for TouchGFX with external RAM on STM32N6 would be very helpful.

Thank you for your support.

Best regards,
Marka

[JohanAstrup]

Hello @siddum.

Yes, the address is determined by the XSPI peripheral. You can see the addresses in Table 2 in the reference manual:

The main consideration when placing framebuffers in external rather than internal RAM is bandwidth. Internal memory offers higher bandwidth due to both higher speed and better efficiency. Whether this matters in practice depends on your display resolution and the amount of pixel operations you perform.

The TBS for the STM32N6570-DK available in TouchGFX Designer is already prepared for using framebuffers in external PSRAM, so you can use it as reference. Remember to set up the correct MPU configuration when using external RAM.

Best regards,
Johan