USB Library
SIGN_FLASH

The SIGN_FLASH command (0x09) causes a special flash signature word to be programmed at a fixed address in the flash memory. The command does not have any data payload. 

Table: SIGN_FLASH command format (sent from host to device)

Packet Byte 
Content 
SIGN_FLASH(0x09) 
1-63 
(padding) 

This command should only be issued once, after a fully completed (and successful) erase/program/verify operation on all memory regions intended to be reprogrammed. The command should be followed by a QUERY_DEVICE command so as to ‘poll’ for the completion of SIGN_FLASH command request.

MLA - USB Library Help Version : 2.16
http://www.microchip.com/mla