Object: POUs for Implicit Checks

You can add these special POUs to an application to provide them with implicit monitoring functions. At runtime, these functions check the limits of arrays or subrange types, the validity of pointer addresses, and division by zero. Note: This option can be disabled for devices that are already equipped with these kinds of monitoring blocks by a special implicit library.

The “Add Object POU for Implicit Checks” command is used to add it to the application. The command opens the “Add POU for Implicit Checks” dialog where you can select a monitoring function type (see table below). Depending on the monitoring function, you have to edit the implementation code or create it yourself from scratch.

To prevent multiple inclusions, monitoring functions that have already been inserted are disabled in the “Add POU for Implicit Checks” dialog.

For more information, see: ⮫ “Using POUs for Implicit Checks ”

NOTICE

To get the feature for monitoring functions, do not edit the declaration part. However, you are permitted to add local variables.

After removing an implicit monitoring function (example: ‎Check Bounds‎) from the project, only a download is possible, not an online change. A corresponding message is displayed.

By default, CODESYS does not run implicit checks for function blocks from libraries used in the application. However, you can extend the check to the libraries by opening the “Properties” dialog of the application and specifying the compiler definition ‎checks_in_libs‎ in the “Compiler Defines” field on the “Build” tab. This definition affects implementation libraries (‎*.library‎) only, not protected libraries (‎*.compiled-library‎).

You can use the "no_check" attribute to deactivate the check for special POUs in the project.

Table 582: Available Functions
Monitoring function	Type
“CheckBounds”	“Bound Checks” Appropriate handling of bound violations; such handling includes setting flags or changing field indices
“CheckDivDInt”	“Division checks”: Monitors the divisor value to avoid division by zero
“CheckDivLInt”
“CheckDivReal”
“CheckDivLReal”
“CheckRangeSigned”	“Range checks”: Monitors the range limit of a subrange type in runtime mode Valid for data types `‎DINT‎`/`‎UDINT‎`
“CheckRangeUnsigned”
“CheckLRangeSigned”	“L-range checks”: Monitors the range limit of a subrange type in runtime mode Valid for data types `‎LINT‎`/`‎ULINT‎`
“CheckLRangeUnsigned”
“CheckPointer”	“Pointer checks” You are responsible for filling in this function completely with implementation code. See the help page for "POU 'CheckPointer'". The function should monitor whether or not the passed pointer references a valid memory address, and whether or not the orientation of the referenced memory area matches the variable type to which the pointer refers. If both conditions are fulfilled, then the pointer is returned. If not, then `‎CheckPointer‎` should complete an appropriate error handling. `‎CheckPointer‎` monitors the same way as variables of type `‎REFERENCE TO‎`.

POU: CheckBounds
POU: CheckDivInt
POU: CheckDivLInt
POU: CheckDivReal
POU: CheckDivLReal
POU: CheckRangeSigned
POU: CheckLRangeSigned
POU: CheckRangeUnsigned
POU: CheckLRangeUnsigned
POU: CheckPointer