Allen-Bradley Micro800 General Instructions Manual page 47

Chapter 3
Ladder Diagram (LD) elements
Pulse Rising Edge Contact
Pulse rising edge (or positive) contacts support a Boolean operation between a
connection line state and the rising edge of a Boolean variable.
The state of the connection line on the right of the contact is set to TRUE when
the state of the connection line on the left is TRUE, and the state of the associated
variable rises from FALSE to TRUE. The state is reset to FALSE in all other cases.
Example: Pulse Rising Edge Contact
Recommendation: Restrict the use of output variables with edge contacts
We recommend you do not use outputs or variables with a Pulse rising edge
contact (positive) or a Pulse falling edge contact (negative). These contacts are for
physical inputs in a ladder diagram. If you need to detect the edge of a variable or
an output, we recommend you use the R_TRIG/F_TRIG function block, which
is supported and works in any language at any location in your program.
Pulse Falling Edge Contact
Pulse falling edge (or negative) contacts support a Boolean operation between a
connection line state and the falling edge of a Boolean variable.
The state of the connection line on the right of the contact is set to TRUE when
the state of the connection line on the left is TRUE, and the state of the associated
variable falls from TRUE to FALSE. The state is reset to FALSE in all other cases.
Rockwell Automation Publication 2080-RM001D-EN-E - February 2015 47