Understanding The Conventions Used By The Program Editors - Siemens Simatic S7-200 System Manual

S7-200 Programmable Controller System Manual

Understanding the Conventions Used by the Program Editors

STEP 7–Micro/WIN uses the following conventions in all of the program editors:
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A # in front of a symbol name (#var1) indicates that the symbol is of local scope.
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For IEC instructions, the % symbol indicates a direct address.
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The operand symbol "?.?" or "????" indicates that an operand configuration is required.
LAD programs are divided into segments called networks. A network is an ordered arrangement of
contacts, coils, and boxes that are all connected to form a complete circuit: no short circuits, no open
circuits, and no reverse power flow conditions exist. STEP 7–Micro/WIN allows you to create comments
for your LAD program on a network-by-network basis. FBD programming uses the network concept for
segmenting and commenting your program.
STL programs do not use networks; however, you can use the NETWORK keyword to segment your
5
program.
Conventions Specific to the LAD Editor
In the LAD editor, you can use the F4, F6, and F9 keys on your keyboard to access contact, box, and coil
instructions. The LAD editor uses the following conventions:
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The symbol "–––>>" is an open circuit or a required power flow connection.
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The symbol "
cascaded or connected in series.
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The symbol ">>" indicates that you can use power flow.
Conventions Specific to the FBD Editor
In the FBD editor, you can use the F4, F6, and F9 keys on your keyboard to access AND, OR, and box
instructions. The FBD editor uses the following conventions:
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The symbol "–––>>" on an EN operand is a power flow or operand indicator. It can also depict an
open circuit or a required power flow connection.
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The symbol "
cascaded or connected in series.
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The symbols "<<" and ">>" indicate that you can use
either a value or power flow.
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Negation bubbles: The logical NOT condition or
inverted condition of the operand or power flow is
shown by the small circle on the input. In Figure 5-5,
Q0.0 is equal to the NOT of I0.0 AND I0.1. Negation
bubbles are only valid for Boolean signals, which can
be specified as parameters or power flow.
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Immediate indicators: As shown in Figure 5-5, the FBD editor displays an immediate condition of a
Boolean operand with a vertical line on the input to an FBD instruction. The immediate indicator
causes an immediate read from the specified physical input. Immediate operators are only valid for
physical inputs.
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Box with no input or output: A box with no input indicates an instruction that is independent of power
flow.
Tip
The number of operands can be expanded up to 32 inputs for AND and OR instructions. To add or
subtract operand tics, use the "+" and "–" keys on your keyboard.
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" indicates that the output is an optional power flow for an instruction that can be
" indicates that the output is an optional power flow for an instruction that can be
Logical NOT
Condition
Immediate
Condition
Figure 5-5 FBD Conventions