Siemens SIMATIC S7-200 - LAD Diagram of Conditional and Unconditional Inputs

Conventions for S7-200 Instructions
8-5
S7-200 Programmable Controller System Manual
A5E00066097-02
NEXT
JMP
Instruction that is dependent on power flow
Instruction that is independent of power flow
FBD
JMP
NEXT
LAD
Instruction that is dependent on power flow
Instruction that is independent of power flow
Figure 8-1 LAD Diagram of Conditional and Unconditional Inputs
Instructions without Outputs: Boxes that cannot cascade are drawn with no
Boolean outputs. These include subroutine calls, JMP, CRET, etc. There are also
ladder coils that can only be placed on the left power rail. These include LBL,
NEXT, SCR, SCRE, etc. These are shown in FBD as boxes and are distinguished
with unlabeled power inputs and no outputs.
Compare Instructions: SIMATIC FBD, IEC Ladder, and IEC FBD compare
instructions are shown as boxes although the operation is performed as a contact.
The compare instruction is executed regardless of the state of power flow. If power
flow is false, the output is false. If power flow is true, the output is set depending
upon the result of the compare.
STEP 7-Micro/WIN 32 Conventions: In STEP 7-Micro/WIN 32, the following
conventions apply in all editors:
• Capital letters used for a symbol (ABC) indicate that it is a global symbol.
• The pound character in front of a symbol name (#var1) indicates that the
symbol is of local scope.
• The % symbol indicates a direct address.
• The operand symbol “?” or “????” indicates that an operand configuration is
required.
Ladder Logic Conventions: In the LAD editor, you can use the F4, F6, and F9
keys on your keyboard to access contact, box, and coil instructions. The following
conventions are used in the Ladder Logic editor.
• The symbol “--->>” is an open circuit, or required power flow connection.
• The indicates that the output is an optional powerflow for an instruction
that can be cascaded or connected in series.
• The symbols “<<” or “>>” indicate that you can use either a value or power flow.
• A contact connected to the power rail indicates that the instruction is
independent of powerflow (Figure 8-1).