DDR3 Clock Issue

Viral Chavda

Other Parts Discussed in Thread: AM3358, AM3354

I have interfaced Micron DDR3 (same part as used in AM335X Starter Kit) with AM3354. When i am loading AM335X Starter Kit GEL file, AM3354 is not generating clock for DDR3. When i am using same GEL File to starter kit, Starter kit AM3358 Soc generating proper clock for DDR3. Can you please tell me the possible reason why AM3354 not generating Clock for DDR3?

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi Viral,

Is it a custom board that has the problem?

Best Regards

Biser

0 Viral Chavda over 12 years ago in reply to Biser Gatchev-XID

Prodigy 160 points

Hi Biser,

Thank you for quick reply, Yes it is custom board. I have attached comparison sheet of DDR3 connection of custom board and Starter kit board. Only Difference is DDRRESETn pin is not pulled up with 10K resistor and DDR_VTP pin is floating. 2287.DDR3Connection.xls. Let me know if you need more inputs to identify the problem.

Thanks & Regard

Viral Chavda

0 Biser Gatchev-XID over 12 years ago in reply to Viral Chavda

TI__Guru**** 393215 points

Hi Viral,

Processor DDR_VTP pin MUST be pulled with 50Ohm resistor to GND. Please check carefully AM335X Datasheet section 5.5.2.3 for DDR3 design guidelines. You can also refer to Starter Kit schematics for a reference (http://processors.wiki.ti.com/index.php/AM335x_StarterKit_Board_Design_Files).

Best Regards

Biser

0 Viral Chavda over 12 years ago in reply to Biser Gatchev-XID

Prodigy 160 points

Hi Biser,

Thanks for your valuable reply. I observer one more difference in our schematic that DDR_CKE pin was not pull down with 10K and hence AM3354 was not able to start generating clock, now clock is available on DDR3. I will modify schematic as per your suggestion.

Thanks & Regards

Viral Chavda

0 Biser Gatchev-XID over 12 years ago in reply to Viral Chavda

TI__Guru**** 393215 points

Hi Viral,

Pulldown on CKE is for the purpose of DDR memory entering self-refresh when processor is in low-power mode.

Best Regards

Biser

0 Viral Chavda over 12 years ago in reply to Biser Gatchev-XID

Prodigy 160 points

Hi Biser,

Your valuable inputs regarding DDR_CKEn & DDR_VTP will help me for improve my schematic and hardware revision. Right now, there is no provision in hardware to pull down DDR_VTP with 50Ohm. Can i go ahead keeping DDR_VTP floating? Will DDR3 misbehave because of DDR_VTP floating?

Thanks & Regards

0 peaves over 12 years ago in reply to Viral Chavda

TI__Guru 63125 points

The DDR PHY in AM335x requires this resistor to calibrate the DDR IO drivers to set constant predetermined output driver impedance. The controller operates by comparing driver impedance to the external reference resistor and adjusting driver impedance to obtain an impedance match.

Regards,
Paul

0 Viral Chavda over 12 years ago in reply to peaves

Prodigy 160 points

We have made changes of DDR3 register as describe in below links.

http://processors.wiki.ti.com/index.php/AM335x_EMIF_Configuration_tips#On_Die_Termination_.28ODT.29_control_of_the_DDR_Device

http://processors.wiki.ti.com/index.php/AM335x_DDR_PHY_register_configuration_for_DDR3_using_Software_Leveling.

Now when i am running DDR3 at 303MHz using GEL file and it pass read/write operation for initial 1k address space of DDR3 but when i am checking for more memory read/write operation it always fails. now when i am running DDR3 at 200MHz using GEL file and it can pass all memory location read/write operation. Can anyone reply what is possible reason for failure in 303MHz?

Thanks & Regards

Viral Chavda

0 Biser Gatchev-XID over 12 years ago in reply to Viral Chavda

TI__Guru**** 393215 points

Hi Viral,

A lot of things could be wrong - EMIF programming, schematics errors, layout errors.

0 Viral Chavda over 12 years ago in reply to Biser Gatchev-XID

Prodigy 160 points

Hi Biser,

I have done software leveling as per describe in wiki link. Now by register setting of DDR3 in GEL file, it is working fine at 303MHz using JTAG. I have modified all DDR3 registers in u-boot and all are same as GEL file. But still DDR3 is not working at 303MHz, however it is working fine at 200MHz with same register setting, I am unable to identify reason. Please help me to figure out the problem.

Regards

Viral Chavda.

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DDR3 Clock Issue