AM3358: DDR speed adjustment

Brian Antheunisse

Part Number: AM3358

Team,

Urgent question here. My customer is about to go to production with a AM3358 based product, but they have hit a snag. Without going too much into details, the question boils down to this:

The datasheet mentions that the minimum DDR speed is about 300MHz, and max is 400MHz. However, there are no instructions we have found in the documentation that explain how to actually adjust the DDR clock speed.

Can you adjust the PLL settings to reduce the DDR speed to below 400MHz? If so, how?

Thanks,

Brian

over 7 years ago

0 Biser Gatchev-XID over 7 years ago

TI__Guru**** 393215 points

Is your customer aware that they need to configure the EMIF and perform software leveling as described here:
processors.wiki.ti.com/.../AM335x_EMIF_Configuration_tips
processors.wiki.ti.com/.../AM335x_DDR_PHY_register_configuration_for_DDR3_using_Software_Leveling

What software are they using?

0 Brian Antheunisse over 7 years ago in reply to Biser Gatchev-XID

TI__Expert 5305 points

Not sure what you mean by what software, but it is a Linux system.

they have seen those pages, and performed the SW leveling and everything. They ended up failing some radiated emissions testing and found out that (I'm not sure why), they cannot emit anything from 399.9MHz to 410MHz. So, their DDR3 that was running at 400MHz needs to be changed. If possible, they would like to just move it to something like 399.7MHz or something like that. There is a lot of mention of 303MHz in those pages as an option, not ideal since they only need to move a little bit. All of those registers in the excel tool and in the wiki page control some sort of latency between clock pulses. What's not clear is how to actually change the fundamental frequency of the clock.

Can someone help us figure this out?

0 Biser Gatchev-XID over 7 years ago in reply to Brian Antheunisse

TI__Guru**** 393215 points

They need to reconfigure the DDR PLL. This is configured in the SPL/MLO bootloader, before U-boot is loaded. I don't know which Linux SDK they use, for the old SDK 6.0 it's described here: processors.wiki.ti.com/.../Sitara_Linux_Training:_Tuning_the_DDR3_Timings_on_BeagleBoneBlack

Processors

Processors forum

AM3358: DDR speed adjustment