The ISP flash application will update your firmware.
This is an ISP module for ATMEL Microcontroller that support ISP such AT89SXXXX, AVR families etc. Requires no power supply because it use power supply from target board. This circuit need only 10 resistors, 1 IC, 1 Capacitor,1 R-Pack.PCB size 1.6 X 4.1 cm. and Plated-Through-Hole type.