mega128的bootload, 支持flash(128k)读写,eepron读写,外部扩展rom读写, 主机可发命令提高波特率,可发命令重启.编译环境IAR for AVR4.20-mega128 of bootload, support flash (128k) to read and write, eepron read and write, read and write rom external expansion, the host can send commands enhance