regarding the config of ddr3

LIANG WANG102707

Expert 1415 points

I am looking the code of uboot in version 06.0.0.0

I found that the startkit which use the ddr3 mt41j128m16,it is configured that the clock output is 303MHz,

but the beagleboneblack which use ddr3 mt41k256m16,it is configured that the clock out out is 400MHz.

I look the datasheet of the two ddr3 chip,I found that both of the two chip the board mounted is data rate 1600 MT/S.

why the uboot code configure them with different clock output ?

Can anyone tell me?I am new of DDR3

thank you.

over 11 years ago

0 Biser Gatchev-XID over 11 years ago

TI__Guru**** 393215 points

The Starter Kit code was developed much earlier than the BB Black and 400MHz operarion was not yet validated back then. 400MHz DDR3 clock is the maximum frequency that the AM335X can support. If you use DDR3 memory on your board you should perform a tuning procedure. These pages describe how it has to be done:

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

http://processors.wiki.ti.com/index.php/AM335x_DDR_PHY_register_configuration_for_DDR3

There is also a step-by-step tutorial here:

http://processors.wiki.ti.com/index.php/Sitara_Linux_Training:_Tuning_the_DDR3_Timings_on_BeagleBoneBlack

0 LIANG WANG102707 over 11 years ago in reply to Biser Gatchev-XID

Expert 1415 points

Dear Biser:

Do you mean that the ddr3 chip on starter kit can support clock in 800MHz,but am335x can only support 400Mhz?

There are two chips of mt41k256m8 on my board to make up an 16bit data line.

What are the differences to only one chip?

thank you

Best regards

wangl

0 Biser Gatchev-XID over 11 years ago in reply to LIANG WANG102707

TI__Guru**** 393215 points

Yes, this is correct. The AM335X can support DDR3 clock frequencies in the range from 303MHz to 400MHz. As to the other question, you can use either 2x8-bit memories or 1x16-bit. Either way you need a 16-bit data bus and the AM335X DDR interface has only 1 chip-select signal. All this is described in section 5.6.2.3 of the AM335X Datasheet, Rev. F.

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regarding the config of ddr3