For 8 digits it requires very large lookup table indeed.
If I spend the rest of my life filling it up, it will work in the end. unless I find some mechanical way of doing it. but the memory blocks of the fpga will be all gone.
The way to do it after some search in xilinx web site is that BCD data is parallel loaded into a modified shift register that successively halves its contents. The equivalent binary value is obtained serially, LSB first, from the LSB of the shift register. it is explained in one of xilinx app notes XAPP029 - Serial Code Conversion between BCD and Binary. http://direct.xilinx.com/bvdocs/ap...app029.pdf
Mahmood