H743 SDRAM memory failure

[matt-crc]

Hello,

I'm using a STM32H743 and IS42S32160 SDRAM.  The SDRAM is in bank1, and I followed the instructions on how to setup the external memory from this guide:

https://community.st.com/t5/stm32-mcus/how-to-set-up-the-fmc-peripheral-to-interface-with-the-sdram/ta-p/49457

i can read/write the entire bank (64Mbytes) one word at a time, but then when I run a memory test, where it uses a pattern (incrementor) at each location the memory test fails.  Also, in debug mode, when I step through the program and watch the memory window, i noticed weird things happening.  Before this memory tests starts, the entire 64mb is initialized to x80000000 as shown below:

Now the first write happens to location 0xc000_0000 <= 0000_0001, which seem to write there, but it also writes or reads  from addresses:  C000_0020, C000_0080, C000_00A0

Something similar happens to the next memory locations:

....

etc... it does that through out the entire memory space.  I checked the schematic, and all the address lines seem to be routed properly (and i was able to initialize the sdram), so I don't think it is that.  I tried this memory test program on multiple boards, exact same issue on all.

The memory clock is setup as per the aforementioned document (200Mhz / 2)

I double checked the timing as per the document and everything seems to be ok.

Anyone have any suggestions?

thanks

Matthew

[matt-crc · Accepted solution]

ok, it seems there was unetched piece of copper between A7 and A5 on all the boards.  I removed that small piece of copper and it seems to be working properly.

thanks