The Arduino Soft Core is the combination of the AVR8 Soft Processor and the Arduino IDE modified to run on the Open Source Papilio FPGA development board.
For more information visit http://papilio.cc
The AVR8 Soft processor was originally downloaded from OpenCores.com.
The Arduino IDE is modified to merge sketches into the AVR8 processor and load the processor and sketch the the Papilio One FPGA dev board.
Please use file "Papilio_AVR8_500K.xise" and not "Papilio_AVR8-500K.xise" - this can create problems.
To synthesize using Xilinx Webpack navigate to the scripts/XilinxISE directory.