Unexpected waveform on STM32H750XBH6 FMC_Dx lines when interfacing with IS42S32400J SDRAM

supen · ‎2025-10-29

Hi,

I'm using an STM32H750XBH6 with an ISSI IS42S32400J-6BL, but the read/write operations keep failing.
I’ve tried setting the CLK to 166 MHz / 120 MHz / 100 MHz / 50 MHz, but it still fails.

When measuring with an oscilloscope, I found that the FMC_Dx pins of the STM32H750XBH6 show an extra waveform in addition to the normal data waveform during output.
I disconnected the 22 Ω series resistors, but the same waveform can still be observed on the MCU’s FMC_Dx pins.

Does anyone know what might be causing this?

pic 1

KDJEM.1 · ‎2025-10-30

Hello @supen and welcome to the community;

Ensure that the hardware setup and clock frequency are correctly configured and verify signal integrity.

Could you please try to configure the IO speed very high.

Thank you.

Kaouthar

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