Siemens STEP 7 Item Syntax
Siemens STEP 7 Item Syntax
The following support for Siemens STEP 7 Variable Table (VAT) syntax is considered to be limited. Care must be taken as the data type for a given S7 data type/suffix may differ from the data type for the same S7 data type/suffix in the specified product. S7 data types not included below are not supported by this driver. The following information is intended to be a guideline for users that are already familiar with and/or prefer the syntax of the specified product. For preferred item syntax, refer to Standard S7-300/400/1200/1500 Item Syntax.
Address Syntax
Input, Output, Peripheral, Flag Memory Types
<memory type><S7 data type><address>
Timer and Counter Memory Types
<memory type><address>
DB Memory Type
DB<num>.<S7 data type><address>
where <num> ranges from 1 to 65535.
See Also: ExamplesMemory Types
Memory Type | Description | Address Range | Data Type | Access |
|---|---|---|---|---|
I E | Inputs | Dependent on S7 Data Type | Read / Write | |
Q A | Outputs | Read / Write | ||
PI PE | Peripheral Inputs | Read Only | ||
PQ PA | Peripheral Outputs | Read / Write | ||
M F | Flag Memory | Read / Write | ||
DB | Data Blocks | Read / Write | ||
T | Timers | T0-T65535 | DWord, Long | Read / Write |
C Z | Counters | C0-C65535 Z0-Z65535 | Word, Short | Read / Write |
See Also: ExamplesAccessing Structured Elements in STEP 7
For the Siemens S7-1200 model, STEP 7 accesses the Counter and Timer structured elements as complete whole structures instead of individual tags. For more information on the element offset and its server address equivalent, refer to the tables below.
Counters
Element | Data Type | Offset | Server Address Equivalent |
|---|---|---|---|
Count_UP | Boolean | 0.0 | DB1,C00.0 |
Count_Down | Boolean | 0.1 | DB1,C00.1 |
Reset | Boolean | 0.2 | DB1,C00.2 |
Load | Boolean | 0.3 | DB1,C00.3 |
Q_UP | Boolean | 0.4 | DB1,C00.4 |
Q_Down | Boolean | 0.5 | DB1,C00.5 |
PAD | Byte | 1.0 | DB1,B1 |
Preset_Value | Short | 2.0 | DB1,I2 |
Count_Value | Short | 4.0 | DB1,I4 |
Timers
Element | Data Type | Offset | Server Address Equivalent |
|---|---|---|---|
Start | DWord | 0.0 | DB1,D0 |
Preset | DWord | 4.0 | DB1,D4 |
Elapsed | DWord | 8.0 | DB1,D8 |
Running | Bool | 12.0 | DB1,DBX12.0 |
IN | Bool | 12.1 | DB1,DBX12.1 |
Q | Bool | 12.2 | DB1,DBX12.2 |
PAD | Byte | 13.0 | DB1,DBB13 |
PAD_2 | Byte | 14.0 | DB1,DBB14 |
PAD_3 | Byte | 15.0 | DB1,DBB15 |
For more information, refer to Standard S7-300/400/1200/1500 Item Syntax.S7 Data Types
The S7 data type is used to coerce the data type for a tag. It does not apply to Counters and Timers. The default data types are shown in bold.
Data Type | Description | Address Range | Data Type | Suffix | Data Type w/ Suffix |
|---|---|---|---|---|---|
None* DBX** | Bit | 0.b-65534.b DBX0.b-DBX65534.b .b is Bit Number 0-15 | Boolean | ||
B DBB** | Unsigned Byte | B0-B65535 DBB0-DBB65535 | Byte, Char | ||
W DBW** | Unsigned Word | W0-W65534 DBW0-DBW65534 | Word, Short, BCD | ||
D DBD** | Unsigned Double Word | D0-D65532 DBD0-DBD65532 | DWord, Long, LBCD, Float | F | Float |
*No S7 data type specified. Applies to non-DB memory types only.
**Applies to DB memory types only.
See Also: ExamplesExamples
S7 Data Type | Data Type | Input | Flags | Data Blocks |
|---|---|---|---|---|
None DBX | Boolean | I0.7 ---- | M0.7 ---- | ---- DB1.DBX0.7 |
B DBB | Byte | IB0 ---- | MB0 ---- | ---- DB1.DBB0 |
W DBW | Word | IW0 ---- | MW0 ---- | ---- DB1.DBW0 |
D DBD | DWord | ID0 ---- | MD0 ---- | ---- DB1.DBD0 |
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Note: The offset for an atomic type tag in a data block is denoted by the column "Address" in Step 7, as shown above. This offset is denoted by the column "Offset" in the Siemens TIA Portal programming environment.