How to issue a MRS command to DDR3 SDRAM from AM335x

Hi Daisuke,

If the DDR is in self-refresh it will not accept commands from the processor. I don't think the SDRAM Config register can be changed on the fly anyhow.

Hi Biser,

Thank you for your reply.

The DDR is not in self-refresh mode.

Section 7.3.3.11.2 in TRM (SPRUH73J) describes as follows:

  "Exit sequence of self-refresh mode for DDR3 device: The memory controller:"

  "If the REG_DDR_DISABLE_DLL bit in the SDRAM Config register is 1, issues a LOAD MODE
   REGISTER command to the extended mode register 1 with the pad_a_o bits set as follows:"

I have found only this about how to issue a MRS command.

Best regards,

Daisuke

I don't think there is any way to issue this command under user control. I think this is part of the EMIF controller state machine.

Hi Biser,
 
Thank you for your reply. Sorry for my late reply.

It does not need to issue this command under user control.

I checked the wiki page.

http://processors.wiki.ti.com/index.php/AM335x_EMIF_Configuration_tips#EMIF_General_Configuration_Registers

If the SDRAM Config register is set, is the MRS command promptly issued to write the mode registers of the memory device?

Best regards,
 
Daisuke