Time-Based Scheduling

Solver, sample rates and transitions, tasking, and real-time execution

Design models for algorithms that depend on time-based scheduling and for which you intend to generate code. Assess usage of continuous and discrete blocks. Use fixed-step solvers for models that run at one or more sample rates. Choose between single-tasking and multitasking execution modes. Identify and handle sample rate transitions within a model.

Topics

Time-Based Scheduling and Code Generation
Consider continuous and discrete block usage, sample times, rate transitions for multirate models, discretization, and choosing between single-tasking mode and multitasking mode when designing models intended for code generation.
Periodic and Aperiodic Function Interfaces
Generate callable entry-point functions for the algorithm represented by a top model.
Rate Transitions and Data Transfers
Handle transitions between blocks with different aperiodic sample rates.
Configure Time-Based Scheduling
Configure the solver type, solver, fixed-step size, periodic sample time constraints, and solver diagnostics for code generation.
Execution of Code Generated from a Model
Execute code generated from single-tasking and multitasking models for rapid-prototyping and embedded system run-time environments.
Tasking Modes and Execution Order
Example that shows task execution order for blocks in a model when configured for single-tasking versus multitasking execution.
Optimize Multirate Multitasking Execution for RTOS Target Environments
Improve performance of generated code by using real-time operating system (RTOS) task management mechanisms to eliminate redundant scheduling calls for multirate, multitasking models.

Featured Examples

Single-Rate Modeling (Bare Board, No OS)

Code generation for a single-rate discrete-time model configured for a bare-board target (one with no operating system).

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Multirate Modeling in Single-Tasking Mode (Bare Board, No OS)

The code generated for a multirate discrete-time model configured for single-tasking on a bare-board target (one with no operating system).

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Multirate Modeling in Multitasking Mode (Bare Board, No OS)

The code generated for a multirate discrete-time model configured for a multitasking bare-board target (one with no operating system).

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Multirate Modeling in Multitasking Mode (VxWorks® OS)

Generates code for a multirate discrete-time model configured for a multitasking operating system target (VxWorks®). The model contains two sample times. Inport block 1 and Inport block 2 specify 1-second and 2-second sample times, respectively, which are enforced by the setting of model configuration parameter Periodic sample time constraint. The solver is set for multitasking operation, which means a Rate Transition block is required to ensure that data integrity is enforced when the 1-second task preempts the 2-second task. Simulink® and the code generator enforce proper rate transitions. This model specifies an explicit Rate Transition block. Alternatively, you can instruct Simulink® to insert this block for you by setting model configuration parameter Automatically handle rate transition for data transfer.

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Trade Determinism and Data Integrity to Improve System Performance

The differences in the operation modes of the Rate Transition block when used in a multirate, multitasking model. The flexible options for the Rate Transition block allow you to select the mode that is best suited for your application. You can trade levels of determinism and data integrity to improve system performance.

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Separate Rate Transition Block Code and Data from Algorithm Code and Data

You can specify whether the code generator inlines code and data it produces for Rate Transition blocks with model code or places the code and data in separate functions that the model code calls. You control this by selecting the Rate Transition block code parameter. Separating Rate Transition block code and data from algorithm code and data enables you to independently analyze, optimize, and test Rate Transition block and algorithm code. By default, Rate Transition block code is set inline with algorithm code and data. You can separate the code and data so that the generated code contains separate get and set functions that the model_step functions call and a dedicated structure for state data. The generated code also contains separate start and initialize functions that the model_initialize function calls.

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