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 Icon |
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. |
or 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. |
or 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. |
or 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. |
or from the context menu |
|
Ctrl + Shift + F3 |
