Siemens SIMATIC S7-1200 - 8.1.3 Positive and negative edge instructions

Basic instructions
8.1 Bit logic operations
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
233
8.1.3
Positive and negative edge instructions
Table 8- 14 Positive and negative transition detection
LAD
FBD
SCL
Description
Not available
1
Scan operand for positive signal edge.
LAD: The state of this contact is TRUE when a positive transition (OFF-
to-ON) is detected on the assigned "IN" bit. The contact logic state is
then combined with the power flow in state to set the power flow out
state. The P contact can be located anywhere in the network except the
end of a branch.
FBD: The output logic state is TRUE when a positive transition (OFF-
to-ON) is detected on the assigned input bit. The P box can only be
located at the beginning of a branch.
Not available
1
Scan operand for negative signal edge.
LAD: The state of this contact is TRUE when a negative transition (ON-
to-OFF) is detected on the assigned input bit. The contact logic state is
then combined with the power flow in state to set the power flow out
state. The N contact can be located anywhere in the network except
the end of a branch.
FBD: The output logic state is TRUE when a negative transition (ON-to-
OFF) is detected on the assigned input bit. The N box can only be
located at the beginning of a branch.
Not available
1
Set operand on positve signal edge.
LAD: The assigned bit "OUT" is TRUE when a positive transition (OFF-
to-ON) is detected on the power flow entering the coil. The power flow
in state always passes through the coil as the power flow out state. The
P coil can be located anywhere in the network.
FBD: The assigned bit "OUT" is TRUE when a positive transition (OFF-
to-ON) is detected on the logic state at the box input connection or on
the input bit assignment if the box is located at the start of a branch.
The input logic state always passes through the box as the output logic
state. The P= box can be located anywhere in the branch.
Not available
1
Set operand on negative signal edge.
LAD: The assigned bit "OUT" is TRUE when a negative transition (ON-
to-OFF) is detected on the power flow entering the coil. The power flow
in state always passes through the coil as the power flow out state. The
N coil can be located anywhere in the network.
FBD: The assigned bit "OUT" is TRUE when a negative transition (ON-
to-OFF) is detected on the logic state at the box input connection or on
the input bit assignment if the box is located at the start of a branch.
The input logic state always passes through the box as the output logic
state. The N= box can be located anywhere in the branch.
1
For SCL: You must write code to replicate this function within your application.