Siemens S7-1200 - Page 210

Basic instructions
7.1 Bit logic operations
S7-1200 Programmable controller
210 System Manual, 03/2014, A5E02486680-AG
Table 7- 15 P_TRIG and N_TRIG
LAD / FBD
SCL
Description
Not available
1
Scan RLO (result of logic operation) for positve signal edge.
The Q output power flow or logic state is TRUE when a positive
transition (OFF-to-ON) is detected on the CLK input state (FBD) or CLK
power flow in (LAD).
In LAD, the P_TRIG instruction cannot be located at the beginning or
end of a network. In FBD, the P_TRIG instruction can be located
anywhere except the end of a branch.
Not available
1
Scan RLO for negative signal edge.
The Q output power flow or logic state is TRUE when a negative
transition (ON-to-OFF) is detected on the CLK input state (FBD) or CLK
power flow in (LAD).
In LAD, the N_TRIG instruction cannot be located at the beginning or
end of a network. In FBD, the N_TRIG instruction can be located
anywhere except the end of a branch.
1
For SCL: You must write code to replicate this function within your application.
Table 7- 16 R_TRIG and F_TRIG instructions
LAD / FBD
SCL
Description
"R_TRIG_DB" (CLK:=
_in_, Q=> _out_
Set tag on positive signal edge.
The assigned instance DB is used to store the previous state of the CLK
input. The Q output power flow or logic state is TRUE when a positive
transition (OFF-to-ON) is detected on the CLK input state (FBD) or CLK
power flow in (LAD).
In LAD, the R_TRIG instruction cannot be located at the beginning or
end of a network. In FBD, the R_TRIG instruction can be located
anywhere except the end of a branch.
"F_TRIG_DB" (CLK:=
_in_, Q=> _out_
Set tag on negative signal edge.
The assigned instance DB is used to store the previous state of the CLK
input. The Q output power flow or logic state is TRUE when a negative
transition (ON-to-OFF) is detected on the CLK input state (FBD) or CLK
power flow in (LAD).
In LAD, the F_TRIG instruction cannot be located at the beginning or
end of a network. In FBD, the F_TRIG instruction can be located
anywhere except the end of a branch.
For R_TRIG and F_TRIG, when you insert the instruction in the program, the "Call options"
dialog opens automatically. In this dialog you can assign
whether the edge memory bit is stored in its own data block (single instance) or as a local
tag (multiple instance) in the
block interface. If you create a separate data block, you will find it in the project tree in the
"Program resources" folder
under "Program blocks > System blocks".