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Observer shawayek
Observer
6,152 Views
Registered: ‎12-13-2013

DDR3 SDRAM tests failing, strange memory problems

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Hello everyone,

 

I am using the ML605 and have built a design that captures the output of an ADC and writes the samples to the onboard DDR3 SDRAM via the AXI DMA. After reading and plotting the data, I observed distortions in the plots. Since I have plotted the ADC data in ChipScope, I know it is captured correctly and that it is a memory problem causing the spikes. The error bits seem to always occur in the same location (in this case, the bits corresponding to one of four channels), most often in one location and never in another. 

 

Seeing this, I looked at the external memory test that I had run when first booting and testing the board, and it doesn't seem to test the SDRAM. I built a base system with no custom design on it, only the basic peripherals, and ran the memory test generated in the applications in SDK. The memory test finds and tests the SDRAM component, but failed at 8, 16 and 32 bits. I tried it with versions 14.1, 14.4 and 14.7. 

 

Can anyone comment on this issue? Do I have a faulty memory chip? 

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Observer shawayek
Observer
10,429 Views
Registered: ‎12-13-2013

Re: DDR3 SDRAM tests failing, strange memory problems

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I found and fixed the problem. The DDR3 chip that came with the board is not only of the wrong size (1GB, thanks for the free 512MB), but also the wrong speed grade (Data rate 1600MT/s instead of the 1066MT/s listed in the BOM). Switching the chip for a 1GB DDR3 that I had in a laptop worked perfectly. Days debugging the memory interface were wasted because the boards are being shipped with different components than what is listed. 

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Observer shawayek
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6,146 Views
Registered: ‎12-13-2013

Re: DDR3 SDRAM tests failing, strange memory problems

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Summary:

 

The BIST preloaded on the board passes for the external memory test.

The memory test application in SDK after correctly building a Microblaze AXI system in EDK fails at 8, 16 and 32 bit tests.

The MIG reference design test fails. I downloaded the prebuilt bit file and ChipScope configuration for the ML605 and the first step (arming the trigger such that it would only trigger if "error" is high" does not pass, since error is high from the start. 

 

What is the problem?

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Observer shawayek
Observer
10,430 Views
Registered: ‎12-13-2013

Re: DDR3 SDRAM tests failing, strange memory problems

Jump to solution

I found and fixed the problem. The DDR3 chip that came with the board is not only of the wrong size (1GB, thanks for the free 512MB), but also the wrong speed grade (Data rate 1600MT/s instead of the 1066MT/s listed in the BOM). Switching the chip for a 1GB DDR3 that I had in a laptop worked perfectly. Days debugging the memory interface were wasted because the boards are being shipped with different components than what is listed. 

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