LoadRetainData block
Short summary
Name |
LoadRetainData |
→POU type |
|
Category |
more system blocks, persistence blocks, block with internal error diagnostic |
Graphical interface |
|
Available since |
The block is supported for the platform WindowsX86 (incl. the built-in PLC under Windows). |
Functionality
The block loads values from a CSV file for →retentive variables.
Restriction
STRING values are only loaded up to the 254th character. Strings > 254 characters are truncated correspondingly.
The values of retentive →function block instances are not loaded.
Recommendation on usage
Use the block only once in a →program and at the beginning of the application cycle (= init state). See example below.
Reason: Depending on the number ob variables and the storage device of the target system, the loading of the values might be rather time consuming. Therefore, if you call this block repeatedly in your application, the execution of the application might take longer with each call.
Inputs, outputs, return value
|
Identifier |
Description |
|
Inputs: |
fileName |
STRING |
name of the file where the values of the variables are stored |
Outputs: |
nrNonLoaded |
INT |
number of variables that could not be loaded |
nrMoreRetainVars |
INT |
number of variables marked as RETAIN in the application for which no values have been not loaded from the file |
|
RC |
UDINT |
return code:
|
|
Return value: |
– |
UDINT |
returns the return code of RC |
Input EN and output ENO are available when →calling
the block. See "Execution control: EN, ENO" for information on input EN and output ENO.
Internal error diagnostic for block
The block checks the following error cases:
The system service has not been loaded.
The return code of the function call equates to an error (output RC ≠ value 0).
In such an error case, the output ENO of the block is set to value FALSE (or an equivalent).
Example for usage within ST-editor
The values of the variables that are declared in the section VAR RETAIN ... END_VAR are loaded in the initial state (= init state) and saved in the term state by using the RTSCycleInfo block.
Best to see the RTSCycleInfo block to find out at which moments the initial cycle and the term cycle respectively are executed.
PROGRAM ExampleLoadSaveRetainData
VAR RETAIN
Test1 : BOOL;
Test2 : INT;
Test3 : REAL;
Test4 : STRING[50];
END_VAR
VAR
init : BOOL;
term : BOOL;
loadRetainRC : UDINT;
loadRetainENO : BOOL;
saveRetainRC : UDINT;
saveRetainENO : BOOL;
nrNonLoaded : INT;
END_VAR
RTSCycleInfo(
Init=>init,
Term=>term
);
LoadRetainData(
EN:=init,
fileName:='Persistent.csv',
nrNonLoaded=>nrNonLoaded,
RC=>loadRetainRC,
ENO=>loadRetainENO
);
SaveRetainData(
EN:=term,
fileName:='Persistent.csv',
RC=>saveRetainRC,
ENO=>saveRetainENO
);
END_PROGRAM
When creating your application within the ST-editor, enter a call of a block by typing the text as requested by the syntax or use Content Assist.