VHDL SDRAM Controller

I’ve tried the SDRAM controller sample, for the XEM3010 demo board.

It works fine, but I’ve noticed the following issue :
it seems that the SDRAM memory controller is OK with the Verilog version, but causes some write/read errors with the Vhdl version.

I’ve tried the 2 versions with the same original PC sample soft (“RAMTester.exe”). It generates no error with the bit file “ramtest-1000.bit” (renamed “ramtest.bit”).

But it gives some erros (about 10 with 90 trials of full SDRAM write/read) with the Vhdl bit file, compiled from the files “VHDL Memory controller”.

Have someone noticed this problem ?
Can you please help me in solving it ?

Many Thanks.

It would seem that the port does not include the 6 synthesis constraints for placing IOB attributes on the SDRAM signals. Without these constraints, the design may not meet timing for the SDRAM interface signals.


Thanks for this information.

But both bitfiles (Verilog and Vhdl) were synthetised with the same constraint file (ucf). I’ve checked this point.

Ive run into the same problem. Have you managed to fix it ?

Yes, but there are a handful of constraints that are specified in the HDL, not in the UCF file. These specify to place FFs in the IOBs.

I have some problem with the SDRAM controller in VHDL. Some times reading from ram or writing to a ram is problematic.
Can you please give me more information about the constraints that are writen in VHDL? I don’t know how to embed them to VHDL.
I would be very appritiate if you can give me the exact directios to write the consraints for the SDRAM controller to vhdl.
Best Regards,


Hello, I’m a beginner with vhdl and opal kelly.

I’m trying to learn how to manage the board memory and i studied the “memory controller” code. It’s time to check if i’m able to make the opal kelly works with the thirdy part example, then i’ll make changes in order to become familiar with the board and vhdl.

I go to the point: i downloaded the vhdl code but the zip file does not contain the RAMTester.exe executable too. Where is the program?

Thank you in advance.


ok, i reply to myself… i found it in samples directory of frontpanel installation.