https://www.automation.siemens.com/mcms/programmable-logic-controller/en/simatic-s7-controller/s7-1500/Pages/default.aspx

https://www.automation.siemens.com/mcms/topics/en/magazines/advance/Documents/advance-2012-4-pn-en.pdf?stc=nls_152_2012011_en

http://www.automation.siemens.com/mcms/programmable-logic-controller/en/simatic-s7-controller/s7-1500/cpu/Documents/s7-1500_techn_data_cpu_en.pdf

Tia Portal v12
http://www.industry.siemens.com/topics/global/en/tia-portal/controller-sw-tia-portal/Pages/Default.aspx