6 User Program  System Manual Modular Systems 
Page 36 of 114  HI 800 191 E Rev. 2.02 
reason, the reaction to this input change is only available at the end of CPU cycle  . 
The reaction time of Prg 2 is two times longer than that of Prg 1. 
Upon completion of the first part   of the Prg 2 cycle under consideration, Prg 2 processing is 
completely aborted and only resumed when   starts. During its cycle, Prg 2 processes the 
data provided by the system during  . The results of Prg 2 are available to the system during 
 (e.g., for process output). The data that the system exchanges with the user program are 
always consistent. 
The program execution order can be controlled by assigning a priority, which indicates how 
important the corresponding user program is compared to the others (see multitasking mode 2). 
To specify the user program execution order, use the following parameters in the resources and 
programs or in the Multitasking Editor: 
A license is required to use the multitasking feature. 
 
Resource, Multitasking 
Editor 
Required or maximum cycle time 
Resource, Multitasking 
Editor 
Use of the execution duration unneeded by the user 
program, e. g., the difference between actual 
execution duration in one CPU cycle and the defined 
Max. Duration for Each Cycle [µs]. 
Resource, Multitasking 
Editor 
The duration of a CPU cycle is based on 
the required execution time of all user 
programs. 
The processor provides user programs 
with a higher priority the execution time not 
needed by user programs with a lower 
priority. Operation mode for high 
availability. 
During the execution time not needed by 
the user programs, the processor waits for 
the time to expire, thus increasing the 
cycle. 
Use of Target Cycle Time [ms]. 
Resource, Multitasking 
Editor 
ID for identifying the program when displayed in 
SILworX 
Importance of a user program; highest priority: 0. 
Program's 
Maximum 
Number of 
CPU Cycles 
Maximum number of CPU cycles required to process 
one user program cycle. 
Max. Duration 
for Each Cycle 
[µs] 
Time permitted for executing the user program within 
a CPU cycle. 
Table 20:  Parameters Configurable for Multitasking 
Observe the following rules when setting the parameters: 
  If Max. Duration for Each Cycle [µs] is set to 0, the execution time of the user program is not 
limited, e.g., it is always processed completely. Therefore, the number of cycles may be set 
to 1 in this case.