text: <s>[INST] Correct way to change a PF drive (ENET) Summary: I need to know which is the best way to make the new drive recognized by PLC when I replace a new one When I have a drive that need to be replace, what i usually did is either these 2 ways : 1. Put the new drive in, config the new IP add, reset the ENET switch (if needed some time) and let the PLC connect to this drive. After that i use RSLogix to access the parameter and config them as my perference 2. Copy the parameter from the existing drive to HIM, replace the drive and transfer it to the new drive. Reset the switch These ways always work for me until one day I can not make the PLC regconize the new drive (Yellow triangle mark) . On the drive, NET A & NET B lamp blinking . I can still ping the drive from the network and see it by RSLinx. After all the efforts (to reset PLC, reset switch, try another drive, redownload the PLC program), i come to the last way : delete the drive out of the IO configuration and add it in again - match drive - redownload the program. Then it work. Could anyone tell me what wrong i am doing to change the drive and what is the best way to do in this case. I really dont want to redownload the program because it make me lost some tag value . Thanks in advance [/INST] This sounds like a firmware mismatch. The plc program is looking for a specific firmware version but your new drive has something different. That you match the drive after deleting it pulls the correct firmware number in. You should flash the drive to the firmware version expected by the plc program to have a more seamless replacement. Alternatively you can disable hardware keying, but i think that will cause you different problems. \\n </s>