EXEC – Real-time executive

Block SymbolLicensing group: STANDARD

Function Description
The EXEC block is a cornerstone of the so-called project main file in the .mdl format, which configures individual subsystems of the REXYGEN system. No similar block can be found in the Matlab-Simulink system. The EXEC block and all connected configuration blocks do not implement any mathematic algorithm. Such configuration structure is used by the REXYGEN Compiler compiler during building of the overall REXYGEN control system application.

The REXYGEN system configuration consists of modules (Modules), input/output drivers (Drivers), archive subsystem (Archives) and real-time subsystem, which includes quick computation tasks (see the QTASK function block description for details) and four priority levels (Level0 to Level3) for inserting computation tasks (see the TASK function block description for details).

The base (shortest) period of the application is determined by the tick parameter. This value is checked by the REXYGEN Compiler compiler as its limits vary by selected target platform. Generally speaking, the lower period is used, the higher computational requirements of the REXYGEN system runtime core (RexCore) are.

The periods of individual computation levels (Level0 to Level3) are determined by multiplying the base period tick by the parameters ntick0 to ntick3. Parameters pri0 to pri3 are the logical priorities of corresponding computation levels in the REXYGEN system. The REXYGEN system uses 32 logical priorities, which are internally mapped to the target platform operating system dependent priorities. The highest logical priority of the REXYGEN system is 0, the value 31 means the lowest. Should two tasks with different priorities run at the same time, the lower priority (higher value) task would be interrupted by the higher priority (lower value) task.

The default priorities pri0 to pri3 reflect the commonly accepted idea that the "fast" tasks (short sampling period) should have higher priority than the "slow" ones (the so-called Rate monotonic scheduling). This means that the default priorities need not to be changed in most cases. Impetuous changes can lead to unpredictable effects!

Outputs

Modules	Output for connecting the REXYGEN system expansion modules, see the MODULE function block description for details	Long (I32)
Drivers	Output for connecting the REXYGEN system input/output drivers, see the IODRV and TIODRV function block descriptions for details	Long (I32)
Archives	Output for archives configuration, see the ARC block	Long (I32)
QTask	Output for connecting quick tasks with the highest priority and the shortest period, see the QTASK block	Long (I32)
Level0	Computation level for inserting tasks (see the TASK block) with high priority pri0 and short period determined by the ntick0 parameter	Long (I32)
Level1	Computation level for inserting tasks with medium priority pri1 and medium-length period determined by the ntick1 parameter	Long (I32)
Level2	Computation level for inserting tasks with low priority pri2 and long period determined by the ntick2 parameter	Long (I32)
Level3	Computation level for inserting tasks with the lowest priority pri3 and the longest period determined by the ntick3 parameter	Long (I32)

Parameters

target	Target device $⊙$ PC - Windows	String
	Generic target device
tick	The base period (tick) of the REXYGEN system core and also the quick task (QTASK) period (in seconds) $⊙$ 0.05	Double (F64)
ntick0	The multiplication tick*ntick0 determines the period of tasks connected to Level0 $↓$ 1 $⊙$ 10	Long (I32)
ntick1	The multiplication tick*ntick1 determines the period of tasks connected to Level1 $↓$ ntick0+1 $⊙$ 50	Long (I32)
ntick2	The multiplication tick*ntick2 determines the period of tasks connected to Level2 $↓$ ntick1+1 $⊙$ 100	Long (I32)
ntick3	The multiplication tick*ntick3 determines the period of tasks connected to Level3 $↓$ ntick2+1 $⊙$ 1200	Long (I32)
pri0	Priority of all Level0 tasks $↓$ 3 $↑$ 31 $⊙$ 5	Long (I32)
pri1	Priority of all Level1 tasks $↓$ pri0+1 $↑$ 31 $⊙$ 9	Long (I32)
pri2	Priority of all Level2 tasks $↓$ pri1+1 $↑$ 31 $⊙$ 13	Long (I32)
pri3	Priority of all Level3 tasks $↓$ pri2+1 $↑$ 31 $⊙$ 18	Long (I32)

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