In older days where M-series PLCs were programmed with DOS version TRiLOGI, there was an option in DOS TRiLOGI to put a transfer password into the PLC to prevent accidental overwriting of PLC program.
This original transfer password protection scheme has been abandoned when Windows version of i-TRiLOGI was introduced in 2001 to avoid confusing user with too many different password schemes (such as TLServer login password, and host link access password control by the TBASIC SETPASSWORD statement).
Under normal operation the PLC would not ask for transfer password. However, if there is a power glitch that corrupts or damages the EEPROM then there is a possibility that a password area inside the EEPROM has been written with some random data and the PLC thinks that a transfer password has been set and will request for it when you try to transfer a program to the PLC.
To clear the transfer password, enter the following command string into the TLServer's Serial Port Setup screen:
@01$cKILL00*
(This is assuming that the PLC ID = 01, please subsitute with your PLC ID if it is not 01). This command will delete the transfer password and clear the program. The PLC will return a response string when the above command is accepted and then you should be able to transfer program to the PLC.
If the above procedure does not clear the password then there is a possibility that the PLC's EEPROM is damaged and it need to be replaced. Please contact Tech support to purchase spare part.
