How do I want to trace or read my FPGA code which has been downloaded to the FPGA. In other words, to read FPGA code to PC. I want to keep that coding as my reference. I'm working with Xilinx software.
The code downloaded to an FPGA is a binary configuration bistream rather than HDL code. As long
as the configuration isn't encrypted, you would be in principle able to recover the gate level netlist
from the bitstream. But the netlist is far from readable HDL code.
Once the code is implemented in the FPGA, there is no return back. You can not read the original HDL code. Actually, the synthesis process converts the HDL code into a gate level netlist.