Sifive freedom-u540 board booting


Hi everybody ,

                    I  am using  freedom-u540 sifive board i want to boot up the board.i have created  bbl.bin inside the work directory using make command. but i want to copy bbl.bin into sd card using dd utility tool . but when i open dd tool inside work directory  bbl.bin file is not showing . so how can i solve this issue.