Applies To:
  • CitectSCADA

The following pop up error message is encountered on starting my Citect project:

"Error 0x21 on opening 'I/O Device Name' for protocol 'Protocol Name'."

A Generic Error 10 and Driver Error 33 (0x21) are displayed in the kernel.


The 0x21 error is described as 'the device specified does not exist'. Often this occurs when a nonexistent port is specified in the ports forms. An example would be specifying a port 2 when there is only a COM1 and COM3 available on the computer. This error may also be the result of another program using one of the same ports as Citect or the same port being defined twice in Citect. The other program may need to be shut down or one of the duplicate ports may need to be deleted.

Note: Errors will pop up even if you are not using that port in the project (setting the device to "Memory" does not resolve the issue).