Operate Blocks and Compare Blocks

Introduction

In addition to the objects defined in IEC 61131-3, there are several other blocks for executing ST instructions and ST expressions and for simple compare operations. These blocks are only available in the LD programming language.

Objects

The following objects are available:

Designation	Representation	Description
Operate block		When the status of the left link is 1, the ST instruction in the block is executed. All ST instructions are allowed except the control instructions: (`RETURN`, `JUMP`, `IF`, `CASE`, `FOR` etc.) For operate blocks, the state of the left link is passed to the right link (regardless of the result of the ST instruction). A block can contain up to 4096 characters. If not all characters can be displayed then the beginning of the character sequence will be followed by suspension points (...). An operate block takes up 1 line and 4 columns. Example: In the example, `Instruction1` is executed if `In1`=1. `Instruction2` is executed if `In1`=1 and `In2`=1 (the result of `Instruction1` has no meaning for the execution of `Instruction2`). Out1 becomes 1 if `In1`=1 and `In2`=1 (the results of `Instruction1` and `Instruction2` have no meaning for the status of `Out1`).
Horizontal Matching Block		Horizontal compare blocks used to execute a compare expression (`<`, `>`, `<=`, `>=`, `=`, `<>`) in the ST programming language. (Note: The same functionality is also possible using ST expressions.) A compare block performs an AND of its left In-pin and the result of its compare condition and assigns the result of this AND unconditionally to its right Out-pin. For example, if the state of the left link is 1 and the result of the comparison is 1, the state of the right link is 1. A horizontal matching block can contain up to 4096 characters. If not all characters can be displayed then the beginning of the character sequence will be followed by suspension points (...). A horizontal matching block takes up 1 line and 2 columns. Example: In the example, `Compare1` is executed if `In1`=1. `Compare2` is executed if `In1`=1 , `In2`=1 a the result of `Compare1`=1. Out1 becomes 1 if `In1`=1, `In2`=1, the result of `Compare1`=1 and the result of `Compare2`=1.

Designation

Representation

Description

Operate block

When the status of the left link is 1, the ST instruction in the block is executed.

All ST instructions are allowed except the control instructions:

(RETURN,
JUMP,

IF,
CASE,
FOR
etc.)

For operate blocks, the state of the left link is passed to the right link (regardless of the result of the ST instruction).

A block can contain up to 4096 characters. If not all characters can be displayed then the beginning of the character sequence will be followed by suspension points (...).

An operate block takes up 1 line and 4 columns.

In the example, Instruction1 is executed if In1=1. Instruction2 is executed if In1=1 and In2=1 (the result of Instruction1 has no meaning for the execution of Instruction2). Out1 becomes 1 if In1=1 and In2=1 (the results of Instruction1 and Instruction2 have no meaning for the status of Out1).

Horizontal Matching Block

Horizontal compare blocks used to execute a compare expression (<, >, <=, >=, =, <>) in the ST programming language. (Note: The same functionality is also possible using ST expressions.)

A compare block performs an AND of its left In-pin and the result of its compare condition and assigns the result of this AND unconditionally to its right Out-pin.

For example, if the state of the left link is 1 and the result of the comparison is 1, the state of the right link is 1.

A horizontal matching block can contain up to 4096 characters. If not all characters can be displayed then the beginning of the character sequence will be followed by suspension points (...).

A horizontal matching block takes up 1 line and 2 columns.

In the example, Compare1 is executed if In1=1. Compare2 is executed if In1=1 , In2=1 a the result of Compare1=1. Out1 becomes 1 if In1=1, In2=1, the result of Compare1=1 and the result of Compare2=1.