Sharp PN-L803C Service Manual page 143

9) Release B1 after checking that the progress bar begins to increase.
Release B1 after beginning to increase from 0%.
10) After a progress bar reaches to 100%, check that LED of touch pen goes out, then click [Cancel].
(When [OK] is clicked by mistake, the process changes to state of writing firmware again. In that case, click [Cancel] to return.)
Check that LED of touch pen goes out.
PN-L803C_80TC3 FIRMWARE UPDATE PROCEDURES 5 - 20