'C' Functions
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'C' Functions

You can write C functions directly in the UniLogic editor, or copy and paste code into the C Editor fields.

Use C functions in the same way you use standard ladder functions. You can call them just like standard ladder functions, reuse them, and export/import them via the Library. You can also refer to Ladder functions.

Note the following limitations:

  1. Within a C function, all of the declared sub-functions must be static, as well all of the global operands.

  2. Within a C function, the size of all of the local variables used in that function and its sub-functions must not exceed 256 bytes.

  3. Float variables are not fully supported. To use floats:

  • Your function must use inputs and outputs of the same data type (floats)

  • Use functions according to the 'C' Functions Float_Macro table shown at the end of this topic.

  1. Division & Modulo operations: variable divisors are not currently supported. Use these macros instead:

  • Instead of "c = a / b;" use: "ARITHMETIC_DIV(1, a, b, c);".

  • Instead of "c = a % b;" use: "ARITHMETIC_MOD(1, a, b, c);".

 

To create a function, right-click a module and select Add C Function to open the C code editor.

 

Your C code must compile correctly in a C compiler.

 

The next image shows the Forward Declaration and the Main section of a C function in UniLogic.

Float 'Macro" table

All inputs and outputs of the function must be of the Float data type.

Instead of this

Use this

b = a

STORE(1, a, b)

a > b

 IF_GT(1, a, b)

a >= b

 IF_GT_EQ(1, a, b)

a == b

 IF_EQ(1, a, b)

a != b

IF_NOT_EQ(1, a, b)

a <= b

 IF_LT_EQ(1, a, b)

a < b

 IF_LT(1, a, b)

c = a + b

ARITHMETIC_ADD(1, a, b, c)

c = a - b

ARITHMETIC_SUB(1, a, b, c)

c = a * b

 ARITHMETIC_MUL(1, a, b, c)

c = a / b

ARITHMETIC_DIV(1, a, b, c)

 ++a

ARITHMETIC_INC(1, a)

 --a

ARITHMETIC_DEC(1, a)

b = abs(a)

ARITHMETIC_ABS(1, a, b)

b = sqrt(a)

 L_SQRT(1, a, b)

c = pow(a, b)

L_POWER(1, a, b, c)

b = log(a)

L_LN(1, a, b)

b = log10(a)

L_LOG10(1, a, b)

b = exp(a)

L_EXP(1, a, b)

b = sin(a)

L_SIN(1, a, b)

b = cos(a)

 L_COS(1, a, b)

b = tan(a)

L_TAN(1, a, b)

b = asin(a)

 L_ASIN(1, a, b)

b = acos(a)

L_ACOS(1, a, b)

b = atan(a)

 L_ATAN(1, a, b)

b = sinh(a)

 L_SINH(1, a, b)

b = cosh(a)

 L_COSH(1, a, b)

b = tanh(a)

 L_TANH(1, a, b)

 

Referring to Ladder Functions

In the Properties Window:

  1. Click Functions References to open the list of Ladder functions in the project.

  2. Select the desired functions; the C editor displays the references.

 

Including Used Global Tags

This enables you to view global tags in C via online mode, without having to pass them as a parameter.

In the Properties Window:

  1. Click Used Globals.

  2. Begin typing the global name.

  3. Select the desired globals; click Close.

  4. In the C function, begin typing the name of the desired tag; click to include it in your code.

 

Viewing Tag Values in Online Mode

You cannot run Online Mode and work on a C function at the same time.

When you have finished working on a C function, you can enter OnLine Mode and view the value of individual tags, as well as view all of the struct member values. Those available for viewing appear as hyperlinks; simply click the hyperlinks to view the online values.

 


Viewing Local Tags in OnLine Mode

You can immediately view global tags in online mode. However, in order to view a function's Local tags, you need to first monitor it by right-clicking it in the Ladder that calls the function, and then selecting Monitor as shown in the next image.