Coding optical transceivers
Coding unlocked transceivers
The most optical transceivers with unlocked memory contain EEPROM chip such as 24C02 which stores informtaion about transceiver form factor, wavelength, transmission technology, speedrate, encoding type, vendor name, serial number and etc. That solution presented in a lot of cheap gigabit transceivers and DAC which don't support DDM function. The memory of those transceivers can be rewritten normally without any restriction from the transceiver.
In such transceivers, as a rule, only the A0H page is available for reading, but reading the A2H page returns an error. You need just import a vendor code into the software or edit a generic code from the module, then press Write button to write to such modules. The coding board returns WRITE OK response when the write successfuly done.
You can use the transceiver with updated vendor code after that!
Coding write-protected transceivers
In accordance with the MSA SFF-8472 specification, DDM capable transceivers can be write protected and require entry a 4 byte password to unlock the memory before write any change.
Such modules operate under the control of a special microcontroller, which emulates an EEPROM chip and provides write functionality in I2C slave mode. Also, it can work as a buffer for EEPROM and control Write Protect pin of the memory chip. An attempt to write to such a transceiver without a password or with an incorrect password returns an error - WRITE FAIL.
The software SFPTotal Wizard supports the function to change a write settings and makes able to set a password value to unlock the memory before saving new changes. In addition, the software allows to create complex programming algorithms in the form of scripts. It makes possible to code transceivers that require factory coding method what is incompatible with specification MSA.