0x65 0x00 0x02 0xC0 0x1C 
0xFF 0xFF 0xFF 0xFF 0xAA
0x99 0x55 0x66 0x30 0x00
Listing 1— The bit file generated by Xilinx ISE is about 80 bytes. The 0x00 0x02 0xC0 0x1C is the file size and can be used as synchronization. You can use 0xAA 0x99 0x55… if you want, but you’ll need to backtrack to get the file size.