Selecting Contacts

Introduction

A contact is an LL984 element that transfers a status on the horizontal link to its right side. This status comes from the Boolean AND link of the status of the horizontal link on the left side with the status of the relevant Boolean current parameter.

Information Concerning Variables

The LL984 Editor can display various information concerning variables attached to coils, contacts and function block nodes.

This information can be displayed by tooltip, too.

For further information on how the variables attached to contacts are displayed, please refer to Network Display.

Contact Types

Contact Type	Description	Call via Menu Command	Call via Key
Normally open contact	For normally open contacts, the status of the left link is copied to the right link, if the status of the relevant Boolean actual parameter is 1. Otherwise, the status of the right link is 0.	Edit → New → Normally open contact or Normally open contact from the context menu	F3
Normally closed contact	For normally closed contacts, the status of the left link is copied to the right link, if the status of the relevant Boolean actual parameter is 0. Otherwise, the status of the right link is 0.	Edit → New → Normally closed contact or Normally closed contact from the context menu	Shift+F3
Positive transition-sensing contact	With contacts for detection of positive transitions, the right link for a program cycle is 1 if a transfer of the relevant actual parameter goes from 0 to 1 and the status of the left link is 1 at the same time. Otherwise, the status of the right link is 0. Also see Edge Recognition.	Edit → New → Positive transition-sensing contact or Positive transition-sensing contact from the context menu	Ctrl+F3
Negative transition-sensing contact	With contacts for detection of negative transitions, the right link for a program cycle is 1 if a transfer of the relevant actual parameter goes from 1 to 0 and the status of the left link is 1 at the same time. Otherwise, the status of the right link is 0. Also see Edge Recognition.	Edit → New → Negative transition-sensing contact or Negative transition-sensing contact from the context menu	Ctrl + Shift + F3