SA0166: Maximum number of input/output/VAR_IN_OUT variables

Function	The check determines whether a defined number of input variables (VAR_INPUT), output variables (VAR_OUTPUT) or VAR_IN_OUT variables is exceeded in a function block. You can configure the parameters that are taken into account in the check by double-clicking on the row for rule 166 in the rule configuration (PLC Project Properties > category "Static Analysis" > "Rules" tab > Rule 166). You can make the following settings in the dialog that appears: Maximum number of inputs (default value: 10) Maximum number of outputs (default value: 10) Maximum number of inputs/outputs (default value: 10)
Reason	This is about checking individual programming guidelines. Many programming guidelines stipulate a maximum number of parameters for function blocks. Too many parameters make the code unreadable and the function blocks difficult to test.
Importance	Medium
PLCopen rule	CP23

	Corresponding metrics available The following metrics are available for calculating the input and output variables as part of the metrics table: Number of input variables Number of output variables

Sample:

Rule 166 is configured with the following parameters:

Maximum number of inputs: 0
Maximum number of outputs: 10
Maximum number of inputs/outputs: 1

The following function block therefore reports two SA0166 errors, since too many inputs (> 0) and too many inputs/outputs (> 1) are declared.

Function block FB_Sample:

FUNCTION_BLOCK FB_Sample         // => SA0166
VAR_INPUT
    bIn     : BOOL;
END_VAR
VAR_OUTPUT
    bOut    : BOOL;
END_VAR
VAR_IN_OUT
    bInOut1 : BOOL;
    bInOut2 : BOOL; 
END_VAR