download image.bin to ram

linux_tyro

here is the script to download image.bin to board (RAM).
XFILE=image.bin
PORT=/dev/ttyS0
...
/usr/bin/sx -vv $XFILE >$PORT <$PORT
...

I can understand "$XFILE >$PORT", but don't know why <$PORT is added to the end.
Could anyone help me? Thank you!