8-17
8 CPU Unit Functions
NJ-series CPU Unit Software User’s Manual (W501)
8-3 SD Memory Card Operations
8
8-3-10 Exclusive Control of File Access in SD Memory Cards
Access to files on the SD Memory Card is possible with the following methods.
(1) FTP server
(2) SD Memory Card operation instructions
(3) FTP client communications instructions
(4) File operations from the Sysmac Studio
However, if the same file on the SD Memory Card is accessed from different sources, unintended oper-
ations such as reading a file while it is being written or writing a file while it is being read may occur.
It is necessary to perform exclusive controls in order to prevent multiple accesses to the same file.
The following table shows the combinations of operations that require exclusive controls.
When you use a combination of operations that requires exclusive controls, execute the later process-
ing only after checking that the first processing is finished.
*1 The instructions include the SD Memory Card operation instructions and the FTP client communications
instructions.
8-3-10 Exclusive Control of File Access in SD Memory Cards
First access
Instructions
*1
File Operations from the
Sysmac Studio
FTP server
Reading Writing Reading Writing Reading Writing
Later access
Instruc-
tions
Read-
ing
Exclusive control is per-
formed automatically, and
an error occurs for the
instruction that is executed
later.
Exclusive
control is
not
required.
Perform
exclusive
control.
Exclusive
control is
not
required.
Perform
exclusive
control.
Writ-
ing
Perform
exclusive
control.
Perform
exclusive
control.
File
operations
from the
Sysmac
Studio
Read-
ing
Exclusive
control is
not
required.
Perform
exclusive
control.
--- --- Exclusive
control is
not
required.
Writ-
ing
Perform exclusive control. --- --- Perform
exclusive
control.
FTP server
Read-
ing
Exclusive
control is
not
required.
Perform
exclusive
control.
Exclusive
control is
not
required.
Perform
exclusive
control.
--- ---
Writ-
ing
Perform exclusive control. --- ---
To Next Page
Loading...
Need help?
General
