Motorola SB6121 MAC & serial change

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I bought new modem Motorola SB6121 with oryginal firmware for replace my older modem but my ISP refused activate the modem.
I have UsbJtag NT, USB 2.0 to UART TTL converter, 3M test clip, jumper cables.
Anyone know how to do it?

http://www.haxorware.com/forums/showthre...+spi+flash
http://www.haxorware.com/forums/showthre...+spi+flash

First post contains tutorial & diagrams how to connect to the programmer. I know how.
Second post contains how to setup Forceware when flashing done.
This 2 post no relation to my question.
I don't want to flash with Forceware. I want to keep original Motorola firmware and change HFC Mac & serial only.
Anyway thanks for reply.

Banana brain it will not work that way you still need forceware.