this model (sb5101e) can not flash the modem through the serial port (unlike scientific atlanta 2100R2).
first firmware load into modem can only be done through JTAG -- blackcat (LPT) or usbjtag (USB), because this modem does not have "noisy" bootloader by default (without the noisy bootloader can flash the modem only via JTAG)
first firmware load into modem can only be done through JTAG -- blackcat (LPT) or usbjtag (USB), because this modem does not have "noisy" bootloader by default (without the noisy bootloader can flash the modem only via JTAG)