Generate Stack XML file from Maintenance Planner:

Go to the Tools > Maintenance Planner > Select 'Access Maintenance Planner

If the system is new, click on Plan

Now select on the required Product Version

Select and Check for relevant Software and files

Select for relevant User Interface

Select for SAP KERNEL Version

Select for latest SUM 

Check for O.S option and Confirm selection here

Select files for Dependent and Independent files and Next

Now, observe here Download Stack XML and Push to Download Basket and Next

Finally check for summary

Finally, software is being download in Download Manager