Mitsubishi Electric MELSEC Q Series User Manual page 328

(d) Operations not allowed during file access
During access to files in a standard ROM, standard RAM, SD memory card, or USB device, do not perform the
following operations. Otherwise, data in the SD memory card and USB device may be corrupted or any file
system failure may occur.
• Power OFF
• Reset
• Restarting user CPU
• Unmounting SD memory card and USB device
• Removing SD memory card and USB device
Configure the program to close the file(s) being accessed and perform the above operations when you access
user file(s) in any of the above memories.
(e) The number of files and directories
The maximum number of files and directories that can be created in the root directory of the following
memories are 512.
• Standard ROM
• Standard RAM
However, the maximum number may be reduced depending on file name length and character types.
The maximum number of files and directories that can be created in the root directory of the following
memories mountable to this product varies depending on memory capacity and file system format.
• SD memory card
• USB device
Moreover, the number directories and the number of files in the root directory are 100 or less. Set this number
to 500 or less.
If you store more files or directories than the above-mentioned, the file access time might significantly increase.
Due to this, it may affect the operation of the C controller module and user program.
(f) Creating a directory
Do not create a directory in the root "/" of the C Controller module. Such directory creation processing fails or
an unintended directory may be created. (These errors occur also when transferring a directory to the root "/"
through FTP.)
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