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load2005
Associate III
March 14, 2026
Question

STM32U5A5: smmc enables DPSM when sending CMD8 command.

  • March 14, 2026
  • 1 reply
  • 128 views

HI ALL.

I am using MB1549C board with NUCLEO-U5A5ZJ-Q cpu.

SD card is connected to SDMMC1 pins 4bit mode.

HAL code is generated with CUBE MX.

During SD card initialization CMD8 command is sent.

I see that after it sent some flags are set which relates to DPSM.

But CMD8 does not require data transfer on D0 pin.

So DPSM must not be enabled. But I see these flags in STAR register.

BUSYD0,DPSMACT,DTIMEOUT.

Response is received correctly but why DPSM is enabled and of course timeout error occur because

there is no and should not be data on D0?

Thanks

1 reply

load2005
load2005Author
Associate III
March 15, 2026

This flag problem occur in SD_PowerON function when calling SDMMC_CmdOperCond function.

It sends CMD8. 

After it BUSYD0,DPSMACT,DTIMEOUT flags are set.

I have configured D0 D1 D2 D3 pins to PULL UP and now these flags are not set.

Still I don't understand why DPSM is activated if no data needed to be received?

And how D0 voltage affects DPSM activation?