Industrial Automation
Industrial Automation | Europe


Main > Product Type > Automation Systems > PLCs
Minimize Text   Default    Enlarge Text


Why Can't I Select Symbols When Uploading From The PLC?

To understand the cause and solution for the CX-Programmer error "There is at least one FB or ST/SFC task in the program of the connecting PLC. The symbol table should be uploaded with the program."
CX-Programmer may display a dialog box shown below that prevents uploading a program from the PLC to the computer. The following information can resolve this issue and prevent future occurrences.

This scenario occurs when a program has been previously transferred (downloaded) to a PLC containing Function Blocks in one of the two following ways:
  • Transferring to the PLC without symbols selected



  • Quick Mode is chosen when sending changes of a Function Block online edit
Only the object code is transferred to the PLC in these two methods. The source code/symbols must be transferred to a PLC if programs containing Function Blocks are to be uploaded in the future.
There are two ways to accomplish transferring the source code to prevent this problem. 
  1. Select symbols when downloading the program  


  1. Manually download the source code after an online edit when using Quick Mode. Choose Program - Online Edit - Transfer FB Source. CX-Programmer will prompt to automatically download the source code if an attempt is made to disconnect while only the object code has been transferred with Quick Mode.

Manual method:



CX-Programmer prompt if offline is attempted before source code is transferred:


IMPORTANT: If only the object code is transferred to a PLC and CX-Programmer is suddenly or unexpectedly disconnected from the PLC, it may not be possible to upload a program from the PLC. When making online edits to Function Blocks and using Quick Mode, always download the source code before disconnecting communications with the PLC (going offline). Also, always select symbols when transferring a project that includes Function Blocks.

If a PLC has Function Blocks loaded without symbols or source code, uploading can be difficult. There is a recovery mechanism used by CX-Programmer if an abrupt disconnection occurred after a Quick Mode transfer without transferring the source code. In this case, CX-Programmer will automatically back up the project and include an .FBK file used to re-establish FB source code when opening the affected project. If a PLC program including FBs was transferred without symbols, there may be no way to upload the project successfully - contact your local Omron representative for more information.

In general, Quick Mode should only be used when there are major restrictions on Function Block transfer speeds. Quick Mode is faster, but will not download the necessary source code to the PLC and prevents uploading programs if the source code is never transferred. As a rule, use Normal Mode.
See the CX-Programmer Operation Manual (Cat. No. W447) Section 3-2 for details regarding Normal Mode and Quick Mode.


Comments (View All Comments / Add Comment)

Related Articles
No related articles found.
Created 2013-11-22
Modified 2014-02-17
Views 14035


You are not logged in.