14 WRITING DATA TO THE CPU MODULE
14.2 Online Change
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Range changeable in a single session
The following shows the number of steps and number of ladder blocks which can be changed in a single session.
• Number of ladder blocks in a file: 64 blocks
• Maximum number of steps in a ladder block: 65535 steps
• Total number of steps for all blocks (steps before changes + steps after changes): 364K steps
Reserved area for online change
Reserved area for online change can be set in a program file to address the online change (ladder block) which causes a
change in the program file size. ( GX Works3 Operating Manual)
In addition, if the changed program exceeds the program file capacity (including reserved area for online change) during the
online change (ladder block), the reserved area for online change can be set again if there is space available in the program
memory.
Required free space in the data memory
If the data memory does not have enough free space when the online change (ladder block) is executed, an error occurs. The
free space of the data memory required for the execution of the online change (ladder block) depends on the size of program
files to be changed or the usage of labels.
*1 When the setting of [Convert] [Online Program Change] [Write Program Restore Information] is "Write with Execution Program",
the required free space is equal to the size of the program restoration information.
The size of the program restoration information can be checked from the memory capacity calculation of the engineering tool.
[Tool] [Confirm Memory Size (Offline)]
The following table lists required free space of the data memory (size of program restoration information) for the online
change (ladder block) in the R120PCPU with a firmware version "12" or earlier.
Online change (ladder block) during the boot operation
When the online change (ladder block) is performed while booting from the SD memory card, the corresponding files on the
booting SD memory card can also be changed.
Firmware version of the CPU module Required data memory space
"13" or later Total increased size of the relevant program restoration information
*1
"12" or earlier Size of the program restoration information
Target program of online change (ladder
block)
Required free space in the data memory
When labels are not
used
When labels are used
(200 global labels and 200 local labels are used)
Ladder program of 1K steps Approx. 20K bytes Approx. 40K bytes
Ladder program of 10K steps Approx. 80K bytes Approx. 140K bytes
Ladder program of 100K steps Approx. 550K bytes Approx. 1000K bytes
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