FAQ00931 of Programmable Controllers FAQ

When performing online editing with the CX-Programmer FA Integrated Tool Package, there is no limit to the number of rungs, but the maximum number of words (number of steps) is limited. If the number of words is too great, select a smaller range (thus reducing the number of words) and start online editing again.
With CX-Programmer Ver. 3.1 or higher, the maximum program size that can be handled while online editing is checked not only at file transfer, but it is checked while editing as well. Therefore, a warning message will be displayed if the maximum program size is exceeded during editing.

The SYSMAC Support Software can only simultaneously edit one rung at a time. If that rung exceeds the program size limit, a "program over" error will occur and you will not be able to edit the program.

Limitations for CS/CJ Series Programmable Controllers and CVM1/CV Series Programmable Controllers

The program size limit for CS/CJ Series depends on the communications settings and is 247 steps for toolbus.
The program size limit for CVM1/CV Series depends on the communications settings and is 263 words for toolbus.
Do not edit the program in a way that would cause the maximum cycle time set in Programmable Controllers Setup to be exceeded. If the maximum cycle time is exceeded, a cycle time exceeded error will occur and operation will stop.

Limitations for C Series Programmable Controllers

C Series has a program size limit of 128 words.
A cycle time exceeded error (non-fatal error) will occur for C200H. If this happens, clear the error.