Short summary

Name	`SaveRetainData`
→POU type	→function
Category	more system blocks, persistence blocks, block with internal error diagnostic
Graphical interface
Available since	version 1.92.0 (for logi.CAD 3) and version 3.8.2 of the →runtime system version 3.2.2 (for library `Standard`) – enhancement: added return value, data type of `filename` changed from `STRING[50]` to `STRING`, wider interface, new filing in sub-folder `Persistence` The block is supported for the platform `WindowsX86` (incl. the built-in PLC under Windows). Moreover, this block is supported for these target systems: →Raspberry Pi, →Revolution Pi

Functionality

The block saves the values of the →retentive variables persistently to a CSV file. Compare SaveRetainDataFast block for an alternative.

Restriction

STRING values are only saved up to the 254th character. Strings > 254 characters are truncated correspondingly.
The values of retentive →function block instances are not saved.

Recommendation on usage

Use the block only once in a →program with a →task for which a corresponding long cycletime has been defined. Moreover, best practice is to trigger the block call by a variable declared in the program (see LoadRetainData block).
Reason: Depending on the number ob variables and the storage device of the target system, the saving 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	→Data type	Description
Inputs:	`fileName`	`STRING`	name of the file where the values of the variables are stored Without any connected value for this input, the file `persistence.csv` is created. By default, the file is saved to the subdirectory `PLC` of the runtime system installation directory. If you prefer that a different directory is used, contact your system integrator and ask to change the configuration of the system service.
Outputs:	`RC`	`UDINT`	return code: `0`: OK `1`: error during file save operation `3`: error during initialization or no variables marked as `RETAIN` `4`: error during file open `5`: there are unknown variable types `6`: no valid path name `9`: system service not loaded on the target system
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

See LoadRetainData block.

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.