Canon PIXMA MG4200 Series On-Screen Manual page 450

The card slot can be shared by multiple computers, if the machine is connected to a network.
Multiple computers can read files from a memory card in the card slot at the same time.
If your computer joins a domain, the card slot may not be mounted as the network drive.
If you use the memory card stored the large size files or many files, a large amount of card
access may be generated. In this case, the operation in the memory card may be impossible or
slow. Operate after the Access lamp of the machine is lit.
When you access the network drive for the card slot over the network, file names consisting of
eight or less lowercase letters (not including its extension) may be shown in uppercase.
For example, a file name such as "abcdefg.doc" will be "ABCDEFG.DOC", while a name such
as "AbcdeFG.doc" will appear the same.
The file is not actually renamed, but merely appears to be changed.
Select Not writable from PC in Read/write attribute under Device user settings of the
machine to read files from a memory card over a network.
Note
If the following occurs when using the network drive for the card slot over a network, see
Cannot Use the Card Slot.
Cannot access the card slot after the network setup of the card slot is complete
The card slot is disconnected
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