Hi,

I attached here a very simple sample program with Data Logging.

As didactical propose, I just call the relative blocks and mount a Watch Table to the manual command. The block FB1 is used just to evaluate diagnose, it has no influence on the data log functions.

I suggest the follow sequence of commands in the Watch Table:
1 – Set a size for the data loggin: “Nr_Records”=10
2 – Create a File: “Cammand_Create”=1, and after “Cammand_Create”=0
3 – Give values for the logged variables, for example: “Data_Block_1”.Data.Int1 = 123; “Data_Block_1”.Data.real1=4,56;
4 – Write the open values to the File: “Cammand_Write”=1, and after “Cammand_Write”=0Repeat the steps 3 (with different values) and 4, so many times you wish
5 – Open the Internet Browser and give the Ethernet address of the PLC as Address (10.100.120.3).
6 – Browse in Data Logs, and click in Download Icon

Note: this sample program was made with STEP 7 V11 SP1 upd1.
SP1 for STEP 7 V11
http://support.automation.siemens.com/WW/view/en/51696778
Update1 for STEP 7 V11 SP1
http://support.automation.siemens.com/WW/view/en/52258326?Datakey=47071380

Note: the v13 SP1 / V14 versions of this project were publish in a post, here, at 27/sep/2017

Memory resource usage:

● The data logs consume only load memory...."
So if your SD card is used as load memory, there will be the data saved.