не е нужно да навлизаме чак в такива подробности..
производителите са помислили за подобен случай, ето:
1. Prepare the TFTP server and APP ROM

2. Use the RS-232 cable connects to console port

3. Connects the LAN port to your PC RJ-45 network adapter

4. Run the Hyper Terminal program on your PC

5. Power On the gateway

6. Press "Enter" as soon as see the message shows on the screen as the figure shown.

7. Login name: water Password: 3333

8. Press h for the command list

9. Press c to configure the network interface

10. Press y to confirm

11. Wait the gateway rebooting and repeat the step.5 to enter the boot mode

12. Press f to input the ROM file name

13. Press d to downloading ROM file

14. Press p to write APP ROM into Flash Memory

15. Press r to reboot the gateway

пробвал съм го това и работи. успех