This leon3 design is tailored to the Altera NIosII Startix2
Development board, with 16-bit DDR SDRAM and 2 Mbyte of SSRAM.
As of this time, the DDR interface only works up to 120 MHz.
At 130, DDR data can be read but not written.
NOTE: the test bench cannot be simulated with DDR enabled
because the Altera pads do not have the correct delay models.
* How to program the flash prom with a FPGA programming file
1. Create a hex file of the programming file with Quartus.
2. Convert it to srecord and adjust the load address:
objcopy --adjust-vma=0x800000 output_file.hexout -O srec fpga.srec
3. Program the flash memory using grmon:
flash erase 0x800000 0xb00000
flash load fpga.srec
