Siemens SIMATIC PCS 7 Operating Manual page 25

The user program is divided to cyclic interrupt OBs according to the requirements:
● OB
– Very fast applications
– For example connections, such as Quadlog or Modbus
● OB
– Fast F-applications (cyclic interrupt with special treatment)
– For example pressure protection functions
● OB
– (Slow) F-applications
– If there is only one cyclic interrupt for F-applications, then it will be the cyclic interrupt
– For example slow temperature protection functions
● OB
– Fast standard applications
– For example fast control functions
● OB
– Slow standard applications
– For example temperature measurements, visualization functions, enable functions
The following rules apply:
● OB
– One of the cyclic interrupt OBs from OB30 to OB38
– Only certain cyclic interrupt OBs are available, depending on the CPU type.
● T
(T
properties)
● OB
(OB
Possible values are 7 to 18.)
Compendium Part B - Process Safety (V8.2)
Operating Manual, 07/2016, A5E35031794-AB
A
B
C
OB with special treatment.
D
E
to OB :
A E
: T < T < T < T
execution A B C
= The execution time of the cyclic interrupt OBs in ms configured in the CPU
execution
: P > P > P > P
priority A B C
= The priority of the cyclic interrupt OBs configured in the CPU properties.
priority
6.1 Adapting CPU parameters (single F-system)
< T
D E
> P
D E
Configuring S7F/FH hardware
25