Since that SDRAM part on that board might operate at up to 200MHz (check
which speed grade you have), I'd recommend you use milkymist-ng and its
memory controller (ASMIcon) with a 1:2 frequency ratio, e.g. run the SoC
at 83MHz and the SDRAM at 166MHz.
http://www.winbond.com/NR/rdonlyres/16898431-2772-4CEA-8474-7E4AA855555F/0/W9825G6JH.pdf
https://github.com/milkymist/milkymist-ng
You will basically need to:
* modify the PHY so that the data serialization ratio becomes 2 (instead
of currently 4 for DDR).
* adapt the clocking accordingly.
* check the timing and other ASMIcon parameters. You have 2 phases and
32-bit data.
* modify the initialization sequence in the BIOS to send the SDR (not
DDR) sequence and set burst length to 2.
Sébastien
On 01/05/2013 06:22 AM, Troy Benjegerdes wrote:
I've got an XESS Xula2 board ( http://www.xess.com/prods/prod055.php )
and eventually I'm planning on doing a ghetto resistor VGA DAC (like
at
http://devbisme.webfactional.com/blogs/devbisme/2011/06/02/simple-vga-interface-xula-fpga-board
)
But first, I need to figure out how to convert from the current 32
bit SDRAM interface to the 16 bit interface on the board. There's
even an SDRAM controller in vhdl
https://github.com/xesscorp/XuLA2/blob/master/FPGA/XuLA_lib/SdramCntl.vhd
So my question is: What's easier/better? Try to use the vhdl version,
or switch the existing milkymist controller to 16 bit? What verilog file
should I be looking in to make the changes?
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