# TargetLink Function Blocks

-----------------------------

[TOC]

## Why​

To insert a function block in a subsystem will insert a function call in the C code generated from the model.
This will reduce the complexity numbers, increase testability and protect against memory problems if there is an interrupt​ and
the function needs to be saved temporary to the memory.

## How

### ​Insert FUNCTION Block

Insert a green FUNCTION block in the subsystem.
Double click the green block and set "Step function name" to `$N_$B` and "Init function name" to `INIT_$N_$B`.

![function_block](../images/target_link/function_block.jpg)

## Important Aspects in the Model

There are two important aspects that need attention.

### Signal Feedback​​​

When using feedback from one subsystem block to another, it is important to use the unit delay block when one uses function blocks.
Strangely one also needs a [rename block](./naming_convention.md#rename-simulink-block) after,
since the unit delay block in this case can not have a readable signal configuration.

### Model Output Signals

Model output signals, prefix starting with *sVc* and *yVc*, needs to have copies that are local readables,
prefix *rVc* and *xVc*, otherwise they will be removed by the current code optimization.

## Code Example

``` c
Void VcModelName(Void)
{
   /* SLStaticLocalInit: Default storage class for static local variables with initvalue | Width: 8
    */
   static Bool X_SModelName2_UnitDelay1 = 0;

   /* call of function: VcModelName/VcModelName/2_SignalCalc */
   VcModelName_2_SignalCalc();

   /* VcModelName/VcModelName/RenameSignal/InPort */
   xVcModelName_B_ConvEffCmplt = X_SModelName2_UnitDelay1;

   /* call of function: VcModelName/VcModelName/1_Entry */
   VcModelName_1_Entry();

   /* call of function: VcModelName/VcModelName/3_Evaluation */
   VcModelName_3_Evaluation();

   /* TargetLink outport: VcModelName/sVcModelName_rt_CnvnMeasd1 */
   sVcModelName_m_NoxUs = SModelName44_Switch;

   /* call of function: VcModelName/VcModelName/4_Judgement */
   VcModelName_4_Judgement();

​}
#include "MemMap_CVC_STOP.h"

​
/**************************************************************************************************\
 ***  FUNCTION:
 ***      VcModelName_1_Entry
 ***
 ***  DESCRIPTION:
 ***
 ***
 ***  PARAMETERS:
 ***      Type               Name                Description
 ***      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 ***
 ***  RETURNS:
 ***      Void
 ***
 ***  SETTINGS:
 ***
\**************************************************************************************************/
#include "MemMap_CVC_START.h"

Void VcModelName_1_Entry(Void)
{​
```