Ladder Toolbox Functions in ST

UniLogic allows you to call supported Ladder Toolbox functions directly from Structured Text (ST). This lets you use these functions in an ST application without switching to Ladder.

The functions use the same behavior, parameters, and data structures as their Ladder counterparts. For information about what a specific function does and its parameters, see the corresponding Ladder topic.

The following Ladder Toolbox functions are currently supported in ST:

• Data Table functions

• PID functions

The following sections describe how to call these functions from ST and explain any ST-specific considerations.

Calling Ladder Toolbox Functions from ST

Call a Ladder Toolbox function from ST in the same way as any other ST function: FunctionName(Param1, Param2,...)
You can also use named parameters to identify parameters explicitly, reorder them or skip optional ones (NAME:=value) 
As you type a Ladder Toolbox function, the ST editor provides the same IntelliSense features available for other ST functions.

Synchronous vs. Asynchronous Functions

Synchronous functions complete during the scan in which they are called and behave the same way as their Ladder equivalents.

Asynchronous functions start an operation that continues after the function call returns. They use the following calling conventions:

• ASYNC_INSERT_ROW_TO_DTI uses an Async Flag parameter and does not use the RESULT parameter used by the file-transfer functions.

• SD, CSV, and recipe file-transfer functions use a RESULT parameter to report the status of the operation.

For file-transfer functions, RESULT has the following values:

Do not start another file-transfer operation while RESULT is 1. 

Structs

Ladder Toolbox functions use the same data structures in ST as their Ladder counterpart. No changes to the existing data structures are required when using these functions from ST.

Online Monitoring

You can monitor supported Ladder Toolbox function calls while the controller is online. In the ST editor, right click the function call and select Monitor; the editor displays the current values of the variables used by the function call. 

Data Table Functions

The following Data Table functions can be called directly from ST.

FIFO and LIFO

• FIFO - PUSH_FIFO, FRONT_FIFO, BACK_FIFO, POP_FIFO, CLEAR_FIFO

• LIFO - PUSH_LIFO, TOP_LIFO, POP_LIFO, CLEAR_LIFO

For information about FIFO and LIFO Data Tables and the behavior and parameters of these functions, see Ladder DT: LIFO and Ladder DT: FIFO

Example:

Use the parameter-hints window to view the parameters supported by each function.

Indexed Data Tables (DTI)

The following Indexed Data Table functions are supported:

WRITE_ROW_TO_DTI

READ_ROW_FROM_DTI

INSERT_ROW_TO_DTI

REMOVE_ROW_FROM_DTI

CLEAR_DTI

CLEAR_DTI_ROW

FIND_DTI_ROW_VALUE

COPY_ARRAY_TO_DTI_COLUMN

COPY_DTI_COLUMN_INTO_ARRAY

COPY_COLUMN_TO_COLUMN_IN_DTI

SET_COLUMN_IN_DTI

FIND_DTI_COLUMN_VALUE

For information about Indexed Data Tables and the behavior and parameters of these functions, see Ladder - Data Table: Indexed (DTI)

When a function requires a DTI column reference, IntelliSense displays the columns available for the DTI table used in the call.

Example:

Asynchronous DTI Insert

ASYNC_INSERT_ROW_TO_DTI is supported in ST for asynchronous row insertion.

Example:

The final BOOL parameter specifies the Async Flag, Use the same setting as the corresponding Ladder Async Insert Row element. ASYNC_INSERT_ROW_TO_DTI does not use the RESULT parameter used by the file-transfer functions. 

For information about asynchronous DTI insertion, see Ladder - Insert Row to DTI- Asynchronous

PID Functions

The following PID functions can be called directly from ST:

RUN_PID

RESET_ID_AUTOTUNE

PAUSE_INTEGRAL_AND_DERIVATIVE_CALCULATION

FORCE_ERROR_INTEGRAL

RUN_AUTOTUNE

SAVE_PID_AUTOTUNE_DATA

LOAD_PID_AUTOTUNE_DATA

For information about PID control, autotuning, and the behavior and parameters of these functions, see Ladder - PID

PID functions use the same PID_Config and PID_AT_Params structures as their Ladder counterparts.

RUN_AUTOTUNE

The cycle-count parameter of RUN_AUTOTUNE uses the Cycles enum. The available value are:

Cycles.One

Cycles.Two

Cycles.Three

Use the enum member when calling RUN_autotune:

A plain integer cannot be used for the cycle-count parameter:

Use IntelliSense to view and select the available Cycles enum members.

PID Autotune Reset

The supported reset function is RESET_PID_AUTOTUNE. There is no separate general-purpose Reset PID function available in ST.