cg3926r1-sl.pdf

Configuration Guide

CG39-26 Rev: 1 January 1997

APACS® 4-mation™

Ladder Logic Version 4.20 and Higher

CG39-26 CONTENTS

January 1997 i

TABLE OF CONTENTS

SECTION TITLE PAGE

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11.1 DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11.2 RELATED LITERATURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

2.0 LADDER LOGIC ELEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

3.0 POWER RAILS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

4.0 LINK ELEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 4.1 HORIZONTAL LINK ELEMENT (H SHUNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 4.2 VERTICAL LINK ELEMENT (V SHUNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

5.0 CONTACTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15.1 NORMALLY OPEN CONTACT (NOC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15.2 NORMALLY CLOSED CONTACT (NCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15.3 POSITIVE TRANSITION-SENSING CONTACT (PTC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25.4 NEGATIVE TRANSITION-SENSING CONTACT (NTC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

6.0 COILS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.1 COIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.2 SET (LATCH) COIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.3 RESET (UNLATCH) COIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26.4 RETENTIVE (MEMORY) COIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-36.5 SET RETENTIVE (MEMORY) COIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-36.6 RESET RETENTIVE (MEMORY) COIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-46.7 POSITIVE TRANSITION-SENSING COIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-46.8 NEGATIVE TRANSITION-SENSING COIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-56.9 NEGATED COIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

CONTENTS CG39-26

January 1997ii

LIST OF FIGURES

FIGURE TITLE PAGE

2-1 Example Ladder Logic Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

3-1 Ladder Logic Power Rails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

4-1 Logic Flow with Vertical Shunts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24-2 Vertical Shunt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

5-1 NOC and NCC Contact Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25-2 PTC and NTC Contact Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

6-1 Set Coil Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26-2 Positive Transition Sensing Coil Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-56-3 Negative Transition Sensing Coil Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

LIST OF TABLES

TABLE TITLE PAGE

5-1 State of the Normally Open Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15-2 State of the Normally Closed Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15-3 State of the Positive Transition-Sensing Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25-4 State of the Negative Transition-Sensing Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

6-1 State of the Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16-2 State of the Set Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16-3 State of the Reset Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26-4 State of the Retentive Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-36-5 State of the Set Retentive Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-36-6 State of the Reset Retentive Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-46-7 State of the Positive Transition-Sensing Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-46-8 State of the Negative Transition-Sensing Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-56-9 State of the Negated Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

Moore Products Co. assumes no liability for errors or omissions in this document or for the application and use of information includedin this document. The information herein is subject to change without notice.

The Moore logo, APACS, the APACS logo ,QUADLOG and 4-mation are trademarks of Moore Products Co.All other trademarks are the property of the respective owners.

© 1997 Moore Products Co. All rights reserved.

CG39-26 INTRODUCTION

January 1997 1-1

1.0 INTRODUCTION

This Guide provides reference information for the Ladder Logic (LL) language of the 4-mation configurationsoftware. It is intended to be used in conjunction with the configuration procedures located in “Using the4-mation Configuration Software” (document number CG39-20).

This Guide is arranged into the following sections:

C Section 1, Introduction

C Section 2, Ladder Logic Elements

C Section 3, Power Rails

C Section 4, Link Elements

C Section 5, Contacts

C Section 6, Coils

1.1 DESCRIPTION

The Ladder Logic (LL) language is one of the four configuration languages of 4-mation. LL simulateshardwired relay logic . Therefore, it lends itself to the configuration of interlock and interface circuits, etc.

1.2 RELATED LITERATURE

Document categories can be identified by the prefix (e.g. CGxx-xx) of the document number as listed here:

CG = Configuration Guide SG = Software GuideSD = Service Data UM = User's Manual

The following 4-mation and other APACS literature is available from Moore Products Co. Generally, allneeded documentation is supplied with your system. Refer to it as needed or as directed in text.

UM39-6 4-mation Installation and OperationThis is a binder which contains the following documents:

SG39-12 Getting Started with 4-mationCG39-20 Using the 4-mation Configuration Software CG39-21 4-mation Software Messages and Diagnostic Codes

INTRODUCTION CG39-26

January 19971-2

UM39-7 4-mation Function Block LanguageThis is a binder which contains the following documents:

CG39-22 APACS Standard Function BlocksCGQL-3 QUADLOG Standard Function BlocksCG39EVENT-1 Sequence of Event Function BlocksCG39FDI-2 Modbus Master Function Blocks for the APACS ACMCG39FDI-3 Modbus Slave Function Blocks for the APACS ACM

UM39-8 4-mation Ladder Logic, SFC & ST LanguagesThis is a binder which contains the following documents:

CG39-26 Ladder Logic (this document)CG39-27 Sequential Function ChartCG39-28 Structured Text

UM39-9 4-mation, Configuring APACS HardwareThis is a binder which contains the following documents:

CG39-24 APACS I/O Module ConfigurationCGQL-4 QUADLOG I/O Module ConfigurationCG39-25 LIM Configuration

UM39-10 4-mation Application LibrariesThis is a binder which contains the following document:

CG39-23 APACS Basic Application Library

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STARTLEFTLINK

RIGHTLINK

CG39-26 LADDER LOGIC ELEMENTS

January 1997 2-1

2.0 LADDER LOGIC ELEMENTS

Each element in a ladder logic network should be given a reference. A reference is a variable of Boolean datatype that is associated with the element. For example, START is the Boolean variable associated with thenormally open contact element shown below. Refer to “Using the 4-mation Configuration Software”(document number CG39-20) for information on how to enter the reference.

The state of a reference may be different from the state of the ladder logic element. This difference will beexplained in the description of each element. All ladder logic elements assume a reference state of FALSEwhen not assigned a reference.

The Ladder Logic language is configured on a 32 x 32 grid of cells called a sheet. In this language,configuration elements are connected together to perform a specific task. The group of connected elements iscalled a Ladder Logic Network. An example a network is shown in Figure 2-1. The elements permitted inthis type of network include:

C Ladder Logic Elements (e.g. contacts, coils and shunts)C Standard Function Blocks (SFB)C Derived Function Blocks (DFB)C User Defined Function Blocks (UFDB)C Structured Text (ST) statements (However, no selection or iteration statements are permitted)C CommentsC Variables

VariableStandard Function Block

Passed Variableas a reference

Local Variableas a reference Coil

00001055

Derived Function BlockShuntContact

LADDER LOGIC ELEMENTS CG39-26

January 19972-2

FIGURE 2-1 Example Ladder Logic Network

The following sections in this Guide explain each of the ladder logic elements. The ladder logic elements areas follows:

C Power Rails

C Link ElementsHorizontal Link Element (H Shunt)Vertical Link Element (V Shunt)

C ContactsNormally Open Contact (NOC)Normally Closed Contact (NCC)Positive Transition-Sensing Contact (PTC)Negative Transition-Sensing Contact (NTC)

CG39-26 LADDER LOGIC ELEMENTS

January 1997 2-3

C Coils CoilSet (Latch) CoilReset (Unlatch) CoilRetentive (Memory) CoilSet Retentive (Memory) CoilReset Retentive (Memory) CoilPositive Transition-Sensing CoilNegative Transition-Sensing CoilNegated Coil

As appropriate, refer to documents “APACS Standard Function Blocks” (document number CG39-22) or“QUADLOG Standard Function Blocks” (document number CGQL-3) for a description of the standardfunction blocks that can be used in ladder logic diagrams.

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LADDER LOGIC ELEMENTS CG39-26

January 19972-4

CG39-26 POWER RAILS

January 1997 3-1

3.0 POWER RAILS

A ladder diagram contains a vertical line on the left side called the left power rail. A ladder diagram alsocontains a vertical line on the right side called the right power rail. The state of the left power rail isconsidered to be TRUE. No state is defined for the right power rail. The left power rail on a sheet can beextended by connecting horizontal and vertical shunts (explained below) to the right power rail. See Figure3-1.

Connection of elements to the right power rail can be explicit or implied. For example, the right power rail isimplied in Figure 3-1. The position of the right rail defaults to column AF. The rail can be moved closer tothe left rail by from the Main Menu Bar by selecting Options, Resize Sheet.

FIGURE 3-1 Ladder Logic Power Rails

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POWER RAILS CG39-26

January 19973-2

CG39-26 LINK ELEMENTS

January 1997 4-1

4.0 LINK ELEMENTS

Link Elements may be either horizontal (Horizontal Shunt) or vertical (Vertical Shunt). Link Elements havean associated state that can be TRUE or FALSE and are used to make connections between contacts, coils,etc.

4.1 HORIZONTAL LINK ELEMENT (H SHUNT)

A Horizontal Link Element is displayed as a horizontal line that occupies one cell.

H SHUNT

A Horizontal Link Element transfers the state of the element in the cell on its left side to the element in thecell on its right side. This ladder element is not the same as the horizontal wiring element of the FunctionBlock language. The Function Block wiring element can transfer analog and Boolean data and does notindicate state on-line, where as the ladder logic horizontal shunt only transfers Boolean data and does indicatestate on-line.

4.2 VERTICAL LINK ELEMENT (V SHUNT)

A Vertical Link Element is displayed as a vertical line that can connect the elements in two consecutive cellsin the same column.

V SHUNT

The state of the Vertical Link Element is the inclusive OR of the states of the elements on its left side andthose connected to it via V Shunts above and below. For example, the state of the Vertical Link Element willbe FALSE if the states of all the attached elements to its left are FALSE. The state will be TRUE if the stateof any of the attached elements to its left are TRUE. The transfer of state can flow up or down, but only inthe direction which enables the rung logic to continue its flow from left to right. For example, Figure 4-1shows vertical shunts flowing upwards which allows the flow of the rung logic to go from left to right

LINK ELEMENTS CG39-26

January 19974-2

FIGURE 4-1 Logic Flow with Vertical Shunts

Unlike the Horizontal Shunt, the Vertical Shunt does not always occupy a cell exclusively. If a Vertical Shuntwas placed in a cell first, then another object cannot be placed in that cell. However, if another element(contact, horizontal shunt, etc.) existed in a cell, a vertical shunt can be placed there also. Refer the examplein Figure 4-2.

FIGURE 4-2 Vertical Shunt

CG39-26 LINK ELEMENTS

January 1997 4-3

Removing a Vertical Link Element requires a special method. Do not use the [Delete] key as this will deleteall cell contents, not just the Vertical Link Element.

To remove only a Vertical Link Element and preserve the other contents of the cell:

1. On the ladder logic sheet, place the cursor on the cell where the Vertical Link Element is located.

2. Press the Vertical Link Element key [F4] or

Select the Vertical Link Element icon with the left mouse button.

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LINK ELEMENTS CG39-26

January 19974-4

CG39-26 CONTACTS

January 1997 5-1

5.0 CONTACTS

A contact is an element that copies a state to the element on its right side that is equal to the AND of the stateof the element on its left side with the given reference. For memory usage and ACM execution timeinformation on all standard configuration elements, see Appendix A in “Using the 4-mation ConfigurationSoftware” (document number CG39-20).

5.1 NORMALLY OPEN CONTACT (NOC)

The symbol of a NOC is shown below. The state of the left link is copied to the right link if the state of theassociated reference is TRUE. Otherwise, the state of the right link is FALSE. Refer to Table 5-1.

TABLE 5-1 State of the Normally Open Contact

STATE OF THE LEFT LINK STATE OF STATE OFREFERENCE ELEMENT

CONDUCTING TRUE CONDUCTING

NOT CONDUCTING or SATISFIED TRUE SATISFIED

X FALSE NOT CONDUCTING

Where “X” indicates any state.

5.2 NORMALLY CLOSED CONTACT (NCC)

The symbol of a NCC is shown below. The state of the left link is copied to the right link if the state of theassociated reference is FALSE. Otherwise, the state of the right link is FALSE. Refer to Table 5-2.

CONTACTS CG39-26

January 19975-2

TABLE 5-2 State of the Normally Closed Contact


CONDUCTING FALSE CONDUCTING

NOT CONDUCTING or SATISFIED FALSE SATISFIED

X TRUE NOT CONDUCTING


Figure 5-1 contains an example using a Normally Open Contact and a Normally Closed Contact.

In the example the following conditions exist:

When SWITCH is TRUE and B is TRUE, LIGHT2 is TRUE and CONDUCTING When SWITCH is TRUE and B is FALSE , LIGHT1 is TRUE and CONDUCTING

FIGURE 5-1 NOC and NCC Contact Example

5.3 POSITIVE TRANSITION-SENSING CONTACT (PTC)

The symbol of a PTC is shown below. The state of the right link is TRUE for one controller scan when aFALSE to TRUE transition of the associated reference is sensed at the same time that the state of the left linkis TRUE. The state of the right link is FALSE at all other times. Refer to Table 5-3.

N

CG39-26 CONTACTS

January 1997 5-3

TABLE 5-3 State of the Positive Transition-Sensing Contact


CONDUCTING FALSE to TRUE CONDUCTING forChange one scan then NOT

CONDUCTING

NOT CONDUCTING or SATISFIED FALSE to TRUE SATISFIEDChange

X FALSE NOT CONDUCTING


NOTE

Since the PTC conducts for a single scan of the controller and the controller execution speedis greater than the screen update rate, the transitions of the PTC may not be visible whileobserving a configuration on-line.

5.4 NEGATIVE TRANSITION-SENSING CONTACT (NTC)

The symbol of an NTC is shown below. The state of the right link is TRUE for one controller scan when atransition of the associated reference from TRUE to FALSE is sensed at the same time that the state of the leftlink is TRUE. The state of the right link is FALSE at all other times. Refer to Table 5-4.

TABLE 5-4 State of the Negative Transition-Sensing Contact

STATE OF THE LEFT LINK STATE OF STATE OF REFERENCE ELEMENT

CONDUCTING TRUE to FALSE CONDUCTING forChange one scan then NOT

CONDUCTING

NOT CONDUCTING or SATISFIED TRUE to FALSE SATISFIEDChange

X TRUE NOT CONDUCTING


CONTACTS CG39-26

January 19975-4

NOTE

Since the NTC conducts for a single scan of the controller and the controller execution speedis greater than the screen update rate, the transitions of the NTC may not be visible whileobserving a configuration on-line.

Figure 5-2 shows an example of using a Positive Transition-Sensing Contact and a Negative Transition-Sensing Contact.

In the example the following conditions exist:

C If POS experiences a FALSE to TRUE change when SWITCH is TRUE, then LIGHT1 will CONDUCTfor one scan.

C If NEG experiences a TRUE to FALSE change when SWITCH is TRUE, then LIGHT2 will CONDUCTfor one scan.

FIGURE 5-2 PTC and NTC Contact Example

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S( )

CG39-26 COILS

January 1997 6-1

6.0 COILS

A coil copies the state of the link on its left to the link on its right without modification. The coil also storesthe state of the left link into an associated Boolean variable (e.g. reference to a Boolean input, output or otherBoolean variable). For memory usage and ACM execution time information on all standard configurationelements, see Appendix A in “Using the 4-mation Configuration Software” (document number CG39-20).

6.1 COIL

The symbol of a coil is shown below. The state of the left link is copied to the associated reference and to theright link. Refer to Table 6-1.

TABLE 6-1 State of the Coil



NOT CONDUCTING or SATISFIED FALSE NOT CONDUCTING

6.2 SET (LATCH) COIL

The symbol of a Set Coil is shown below. The associated reference is in the TRUE state when the left link isin the TRUE state. The reference, but not the coil, remains set to TRUE until reset by another coil. Refer toTable 6-2.

TABLE 6-2 State of the Set Coil



NOT CONDUCTING or SATISFIED Last State NOT CONDUCTING

The on-line display of the “(S)” part of the element is based upon the state of the reference. For example, ifthe reference is in the TRUE state, then the “(S)” portion of the element will be displayed in theCONDUCTING state color (i.e. the coil is set). The example in Figure 6-1 demonstrates the functionality of

COILS CG39-26

January 19976-2

the Set Coil.

When LATCH_ON is TRUE, the LATCH1 set coil, the LIGHT1 coil, the LATCH1 contact, and the LIGHT2coil are CONDUCTING. If LATCH_ON then turns FALSE, the LATCH1 set coil and the LIGHT1 coil areNOT CONDUCTING, but since the LATCH1 reference remains TRUE, the LATCH1 contact and theLIGHT2 coil remain CONDUCTING. To reset the LATCH1 reference in this example, the referenceLATCH_OFF must become TRUE.

FIGURE 6-1 Set Coil Example

6.3 RESET (UNLATCH) COIL

The symbol of a Reset Coil is shown below. The associated reference is in the FALSE state when the left linkis in the TRUE state. The reference, but not the coil, remains reset to FALSE until set by another coil. Referto Table 6-3.

TABLE 6-3 State of the Reset Coil




The on-line display of the (R) part of the element is based upon the state of the reference. For example, if thereference is in the FALSE state then the (R) portion of the element is displayed in the CONDUCTING statecolor (i.e. the coil is reset).

( )M

CG39-26 COILS

January 1997 6-3

6.4 RETENTIVE (MEMORY) COIL

The symbol of a Retentive Coil is shown below. The state of the left link is copied to the associated referencevariable and to the right link. The retentive feature, which saves the current value through a warm restart, isautomatically activated when a reference is assigned to this coil (the RETAIN check box found on theVariable Declaration dialog box is automatically selected). Refer to Table 6-4.

TABLE 6-4 State of the Retentive Coil




6.5 SET RETENTIVE (MEMORY) COIL

The symbol of a Set Retentive Coil is shown below. The associated reference is set to TRUE when the leftlink is in the TRUE state. The reference remains TRUE until reset by another coil (R or RM). The retentivefeature, which saves the current value through a warm restart, is automatically activated when a reference isassigned to this coil (the RETAIN check box found on the Variable Declaration dialog box is automaticallyselected). Refer to Table 6-5.

TABLE 6-5 State of the Set Retentive Coil




COILS CG39-26

January 19976-4

6.6 RESET RETENTIVE (MEMORY) COIL

The symbol of a Reset Retentive Coil is shown above. The associated reference is reset to FALSE when theleft link is in the TRUE state. The reference remains reset to FALSE until set by another coil (S or SM). Theretentive feature, which saves the current value through a warm restart, is automatically activated when areference is assigned to this coil (the RETAIN check box found on the Variable Declaration dialog box isautomatically selected). Refer to Table 6-6.

TABLE 6-6 State of the Reset Retentive Coil




6.7 POSITIVE TRANSITION-SENSING COIL

The symbol of a Positive Transition-Sensing Coil is shown below. The state of the associated reference isTRUE for one controller scan when a FALSE to TRUE transition of the left link is sensed. The state of theleft link is always copied to the right link. Refer to Table 6-7.

TABLE 6-7 State of the Positive Transition-Sensing Coil


FALSE to TRUE change TRUE for one scan CONDUCTING


CONDUCTING, no change FALSE CONDUCTING

The example in Figure 6-2 demonstrates the functionality of the Positive Transition-Sensing Coil.

CG39-26 COILS

January 1997 6-5

When SWITCH changes from FALSE to TRUE, coil A, coil LIGHT1, contact A and coil LIGHT2 are allCONDUCTING. The very next scan, SWITCH remains CONDUCTING and coil A and coil LIGHT1remain CONDUCTING. However, contact A and coil LIGHT2 are NOT CONDUCTING because thereference of a Positive Transition-Sensing Coil is TRUE for one scan only. If SWITCH becomes FALSE,then the A and LIGHT1 coils are NOT CONDUCTING.

FIGURE 6-2 Positive Transition Sensing Coil Example

6.8 NEGATIVE TRANSITION-SENSING COIL

The symbol of a Negative Transition-Sensing Coil is shown below. The state of the associated reference isTRUE for one controller scan when a TRUE to FALSE transition of the left link is sensed. The state of theleft link is always copied to the right link. Refer to Table 6-8.

TABLE 6-8 State of the Negative Transition-Sensing Coil


TRUE to FALSE change TRUE for one scan CONDUCTING


CONDUCTING, no change FALSE CONDUCTING

The example in Figure 6-3 demonstrates the functionality of the Negative Transition-Sensing Coil.

COILS CG39-26

January 19976-6

When the reference variable SWITCH is TRUE, contact SWITCH, coil B, and coil LIGHT1 areCONDUCTING because the state of the left link is always copied to the right link. Contact B and LIGHT2are NOT CONDUCTING because the reference of a Negative Transition-Sensing Coil is not TRUE unless anegative transition is sensed. When the reference SWITCH transitions from TRUE to FALSE, the B coil,LIGHT1 coil , and SWITCH contact are NOT CONDUCTING, while the B contact and LIGHT2 coil areCONDUCTING. The very next scan, the SWITCH contact, B coil and LIGHT1 coil remain NOTCONDUCTING while the B contact and LIGHT2 coil change to NOT CONDUCTING because thereference of a Negative Transition-Sensing Coil is TRUE for one scan only.

FIGURE 6-3 Negative Transition Sensing Coil Example

6.9 NEGATED COIL

The symbol of a Negated Coil is shown below. The inverse of the left link is copied to the associatedreference variable. The state of the left link is always copied to the right link. Refer to Table 6-9.

TABLE 6-9 State of the Negated Coil



NOT CONDUCTING or SATISFIED TRUE NOT CONDUCTING

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cg3926r1-sl.pdf

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