Parameters to reduce SDRAM power consomption

[mbourhis]

Hi,

The 'DDR memory controller' allows us to choose the 'power management mode'.

In the 'QorIQ LS1028A Reference Manual', I read the 'dynamic power management mode' can reduce power consomption.

My first question is:

does this mode reduce the DDR refresh rate, and is there an impact about the performances?

My second question is how to active this 'power management mode'? Is there a regsiter to write in it, at which step of the boot (with the PreBoot Loader ?)?

Thanks for your help.

Regards,

[Bulat · Accepted solution]

1. When dynamic power management mode is enabled, it puts SDRAM devices into power-down mode when there is no ongoing memory activity by negating CKE signal. Details of 'power-down mode' can be found in SDRAM datasheets.

When the memory exits from the power-down mode, it requires some time delay (tXP) before any bus command (like read/write), so yes, this mode slightly affects performance. 

2. To enable dynamic power management mode the user should set bit DDR_SDRAM_CFG[DYN_PWR]. This can be done any time, for example before the DDR controller is enabled.

Regards,

Bulat