Real-Time Workshop User's Guide

Nonvirtual Subsystem Code Generation Options

For any nonvirtual subsystem, you can choose the following code generation options from the RTW system code pop-up menu in the subsystem Block parameters dialog:

• Auto: This is the default option. See Auto Option below.
• Inline: This option explicitly directs the Real-Time Workshop to inline the subsystem.
• Function: This option explicitly directs the Real-Time Workshop to generate a separate function and (optionally) a separate file for the subsystem. In this case you can choose further options to control the naming of the generated function and file.

The sections below discuss the Auto, Inline, and Function options.

Auto Option

In the current release, the Auto option causes the Real-Time Workshop to inline the subsystem, unless it is a function-call subsystem with multiple callers. In that case, a function is generated.

In a future release, the Auto option will also create functions when multiple instances of a subsystem are detected. If there are multiple instances or multiple callers of the subsystem, the subsystem will not be inlined. To take advantage of this capability, you should choose the Auto option. Choose Inline or Function when you want specifically to inline a subsystem or generate a separate function and code module.

To use the Auto option:

1. Select the subsystem block. Then select Subsystem parameters from the Simulink Edit menu. The Block Parameters dialog opens, as shown in Figure 3-7.

Alternatively, you can open the Block Parameters dialog by:

• Shift-double-clicking on the Subsystem block
• Right-clicking on the Subsystem block and selecting Block parameters from the pop-up menu.

2. If the subsystem is virtual, select Treat as atomic unit as shown in Figure 3-7. This makes the subsystem nonvirtual, and the RTW system code option becomes enabled.

If the system is already nonvirtual, the RTW system code option is already enabled.

3. Select Auto from the RTW system code pop-up menu as shown in Figure 3-7.
4. Click Apply and close the dialog.

Figure 3-7: Auto Code Generation Option for a Nonvirtual Subsystem

Inline Option

As noted above, subsystem code can be inlined only if the subsystem is nonvirtual.

Exceptions to Inlining.   Note that there are certain cases in which the Real-Time Workshop will not inline a nonvirtual subsystem, even though the Inline option is selected. These cases are:

• If the subsystem is a function-call subsystem that is called by a noninlined S-function, the Inline option is ignored. Noninlined S-functions make such calls via function pointers; therefore the function-call subsystem must generate a function with all arguments present.
• In a feedback loop involving function-call subsystems, the Real-Time Workshop will force one of the subsystems to be generated as a function instead of inlining it. The Real-Time Workshop selects the subsystem to be generated as a function based on the order in which the subsystems are sorted internally.
• If a subsystem is called from an S-function block that sets the option SS_OPTION_FORCE_NONINLINED_FCNCALL to TRUE, it will not be inlined. This may be the case when user-defined Asynchronous Interrupt blocks or Task Synchronization blocks are required. Such blocks must be generated as functions. The VxWorks Asynchronous Interrupt and Task Synchronization blocks, shipped with the Real-Time Workshop, use the SS_OPTION_FORCE_NONINLINED_FCNCALL option.

To generate inlined subsystem code:

1. Select the subsystem block. Then select Subsystem parameters from the Simulink Edit menu. The Block Parameters dialog opens, as shown in Figure 3-8.

Alternatively, you can open the Block Parameters dialog by:

• Shift-double-clicking on the Subsystem block
• Right-clicking on the Subsystem block and selecting Block parameters from the pop-up menu.

2. If the subsystem is virtual, select Treat as atomic unit as shown in Figure 3-8. This makes the subsystem atomic, and the RTW system code pop-up menu becomes enabled.

If the system is already nonvirtual, the RTW system code menu is already enabled.

3. Select Inline from the RTW system code menu as shown in Figure 3-8.
4. Click Apply and close the dialog.

Figure 3-8: Inlined Code Generation for a Nonvirtual Subsystem

When you generate code from your model, the Real-Time Workshop writes inline code within model.c to perform subsystem computations. You can identify this code by system/block identification tags, such as the following.

/* Atomic SubSystem Block: <Root>/AtomicSubsys1 */

See Tracing Generated Code Back to Your Simulink Model for further information on system/block identification tags.

Function Option

This option lets you direct the Real-Time Workshop to generate a separate function and (optionally) a separate file for the subsystem. When you select the Function option, two additional options are enabled:

• The RTW function name options menu lets you control the naming of the generated function.
• The RTW file name options menu lets you control the naming of the generated file (if a separate file is generated).

Figure 3-9 shows the Block Parameters dialog with the Function option selected.

RTW Function Name Options Menu.   This menu offers the following choices:

• Auto: the Real-Time Workshop assigns a unique function name using the default naming convention: model_systemid(), where systemid is a sequential identifier (s0, s1,...sn) assigned by Simulink.
• UseSubSystemName: the Real-Time Workshop uses the subsystem name as the function name.
• UserSpecified: When this option is selected, the RTW function name text entry field is enabled. Enter any legal function name. Note that the function name must be unique.

RTW File Name Options Menu.   This menu offers the following choices:

• UseSubSystemName: the Real-Time Workshop generates a separate file, using the subsystem name as the filename.
• UseFunctionName: the Real-Time Workshop generates a separate file, using the function name (as specified by the RTW function name options) as the filename.
• UserSpecified: When this option is selected, the RTW file name (no extension) text entry field is enabled. The Real-Time Workshop generates a separate file, using the name you enter as the filename. Enter any filename desired, but do not include the .c (or any other) extension. Note that this filename should be unique.
• Auto: the Real-Time Workshop does not generate a separate file for the subsystem. Code generated from the subsystem is generated within the code module generated from the subsystem's parent system. If the subsystem's parent is the model itself, code generated from the subsystem is generated within model.c.

To generate both a separate subsystem function and a separate file:

1. Select the subsystem block. Then select Subsystem parameters from the Simulink Edit menu, to open the Block Parameters dialog.

Alternatively, you can open the Block Parameters dialog by:

• Shift-double-clicking on the Subsystem block
• Right-clicking on the Subsystem block and selecting Block parameters from the pop-up menu.

2. If the subsystem is virtual, select Treat as atomic unit as shown in Figure 3-9. This makes the subsystem atomic, and the RTW system code menu becomes enabled.

If the system is already nonvirtual, the RTW system code menu is already enabled.

3. Select Function from the RTW system code menu as shown in Figure 3-9.
4. Set the function name, using the RTW function name options described in RTW Function Name Options Menu.
5. Set the filename, using any RTW file name option other than Auto (options are described in RTW File Name Options Menu).

Figure 3-9 shows the use of the UserSpecified filename option.

6. Click Apply and close the dialog.

Figure 3-9: Subsystem Function Code Generation
with Separate User-Defined File Name

Nonvirtual Subsystem Code Generation

Modularity of Subsystem Code