HIMax System 5 Programming
HI 801 001 E Rev. 4.01 Page 71 of 122
Usually, the individual user programs run concurrently in a non-reactive manner. However,
reciprocal influence can be caused by:
Use of the same global variables in several user programs.
Unpredictably long runtimes can occur in individual user programs if a limit is not
configured with Max Duration for Each Cycle.
NOTE
An unpredictable behavior of the user program is possible!
The use of the same global variables in several user programs can lead to a variety
of consequences caused by the reciprocal influence among the user programs.
Carefully plan the use of the same global variables in several user programs.
Use the cross-references in SILworX to check the use of global data. Global data
may only be assigned values in one location, either in a user program or from the
hardware!
i
HIMA recommends to set the Max. Duration for each Cycle [µs] parameter to an
appropriate value ≠ 0. This ensures that a user program with an excessively long runtime
is stopped during the current CPU cycle and resumed in the next CPU cycle without
affecting the other user programs.
Otherwise, an unusually long runtime for one or several user programs can cause the
target cycle time, or even the resource watchdog time, to be exceeded, thus leading to an
error stop of the controller.
5.4.1 Multitasking Mode
Three operation modes exist for multitasking. These modes differ in how the time that is not
needed for executing the CPU cycle of the user programs is used. One of these three
modes can be selected for every resource.
1. Multitasking Mode 1 uses the unneeded time to reduce the CPU cycle. If the user
program is completely processed, processing of the next user program begins
immediately. In total, this results in a shorter cycle.
Example: 3 user programs (UP 1, UP 2 and UP 3) that allow a user program cycle to
take up to 3 CPU cycles.
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