Operator controls and operating modes of the CPU 410-5H 
  7.3 Self-test 
CPU 410-5H Process Automation/CPU 410 SMART 
System Manual, 10/2013, A5E32631667-AA 
107 
For detailed information on SFC 90 "H_CTRL", refer to Manual 
System Software for S7-
300/400, System and Standard Functions
. 
 
-safe system, you are not allowed to disable and then re-enable the cyclic self-tests. 
For more details, refer to Manual 
 S7-400F and S7-400FH Automation Systems
.