Postby neogator » Tue Jan 11, 2022 8:52 pm
Typically, OEM copper SFPs are based on a simple EEPROM such as the 24C02 and do not have a PCB-mounted MCU that performs write protection function in accordance with SFF 8472.
Often the WP pin is connected to one of the TX or RX power circuits of the transceiver. This trick is used by the manufacturer since the copper modules do not have a laser and an optical receiver.
Your task is to try to break the power lines of the transceiver in turn and try to write to the module every time.
Also TX_DISABLE which is connected to Vcc in normal state is often used to control write protection.
Further blocking options are possible using the TX_FAULT line, it is also useless for a copper transceiver and can be used in vendor special functions to control write protection. In contrast to the above, a logical unit must be sent to the TX_FAULT line.
All of the same is true for DAC cables.
Try all 4 options)