STM32F429 FMC SDRAM DELAY CHANGE

[jacekborko]

Posted on May 10, 2015 at 22:48

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[stm322399]

Posted on May 11, 2015 at 09:48

Bit changes often appears when refresh is not done frequently enough. Remake the math, or simply test with arbitrary faster value.

Just make sure that bits other than D13 and D14 are concerned (wait more time), otherwise we cannot exclude a wiring issue.

[jacekborko]

Posted on May 11, 2015 at 20:59

datasheet says ''Refresh Interval Time  -  max 15.6 '' so :

 //15.6us*84MHz=1311 

when i use 100

  FMC_Bank5_6->SDRTR=100<<1;

this didnt gave any result.

when i put even 

  FMC_Bank5_6->SDRTR=10000<<1;

thats didnt gave any result.

''Just make sure that bits other than D13 and D14 are concerned (wait more time),'' could you explain me this part, and how to check it ?

[Tesla DeLorean]

Posted on May 11, 2015 at 21:32

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Quantify if, and for how long, the bits hold their correct states? ie measure time to observed failure. If time is zero, consider if it's even wired/soldered correctly.

[stm322399]

Posted on May 12, 2015 at 09:33

I mean that in the case you have a problem with refresh, then observing data in SDRAM will lead to bit corruption evenly in any 16-bit word.

After some delay:

d0003d4 fe117206

After a longer delay:

d0003d4 fee5fafe

After a more longer delay:

d0003d4 ffffffff

Depending the DRAM technology, some pages tends to fill with 1's others with 0's

Your example only showed bits D13/14 to be corrupted. Given that DRAM expect tight timings, wiring issues are not excluded (unbalanced capacitive load, long wires, bad grounding, etc...). Normally SDRAM are easy to wire (compared to DDRs), so I assume that the wiring issue should be (more or less) trivial to find. Carefully check pin sharing, pull-up/down, etc ...

[jacekborko]

Posted on May 12, 2015 at 13:36

after first change of value it looks like:

Adress   value

------

2002ffe4 cccccccc

d0000000 eccceccc

and after couple minutes

2002ffe4 cccccccc

d0000000 fcccfccc

when i connected the D13 or D14 pins to the 0 or 1 i saw just additional change in two place  ( fccXfccX ) and the X changed for example in that way:

  00

  11

  22

  33

  40

  51

  62

  73

  88

  99

  aa

  bb

  c8

  d9

  ea

  fb

so maybe  that is not a problem with D13 or D14 pins ?

[jacekborko]

Posted on May 14, 2015 at 08:53

anyone have some suggestions ?