Configuring Variable Tags
- Last UpdatedJul 08, 2025
- 2 minute read
Variable tags are addressed using the symbolic tag names configured for Siemens S7-PLC device. The following table demonstrates the variable tag address formats you can use to read and write values
|
Address Format |
S7-1500 Data Type |
S7-1200 Data Type |
Plant SCADA Type |
Value Range |
|---|---|---|---|---|
|
<Symbolic Tag Name> |
BOOL |
BOOL |
DIGITAL |
FALSE or TRUE |
|
<Symbolic Tag Name> |
BYTE |
BYTE |
INT, UINT, LONG, ULONG |
0 to 255 |
|
<Symbolic Tag Name> |
WORD |
WORD |
UINT, LONG, ULONG |
0 to 65535 |
|
<Symbolic Tag Name> |
DWORD |
DWORD |
ULONG |
0 to 4294967295 |
|
<Symbolic Tag Name> |
SINT |
SINT |
INT, LONG |
128 to 127 |
|
<Symbolic Tag Name> |
USINT |
USINT |
INT, UINT, LONG, ULONG |
0 to 255 |
|
<Symbolic Tag Name> |
INT |
INT |
INT, LONG |
-32768 to 32767 |
|
<Symbolic Tag Name> |
UINT |
UINT |
UINT, LONG, ULONG |
0 to 65535 |
|
<Symbolic Tag Name> |
DINT |
DINT |
LONG |
-2147483648 to +2147483647 |
|
<Symbolic Tag Name> |
UDINT |
UDINT |
ULONG |
0 to 4294967295 |
|
<Symbolic Tag Name> |
REAL |
REAL |
REAL |
-3.4E38 to 3.4E38 |
|
<Symbolic Tag Name> |
CHAR |
CHAR, STRING |
CHAR, STRING |
ASCII character |
|
<Symbolic Tag Name> |
WCHAR |
WCHAR |
STRING |
Unicode character represented as ASCII character in Plant SCADA Note: Driver supports multi-byte strings only when it is possible to convert a multi-byte character to the ASCII. |
|
<Symbolic Tag Name> |
WSTRING |
WSTRING |
STRING |
Unicode string (0-254 characters) represented as ASCII string in Plant SCADA Note: Driver supports multi-byte strings only when it is possible to convert a multi-byte character to the ASCII. |
|
<Symbolic Tag Name> |
S5TIME |
N/A |
LONG |
0 to 9990000 (milliseconds) |
|
<Symbolic Tag Name> - |
TIME |
TIME |
LONG |
-2147483648 to +2147483647 (milliseconds) |
|
<Symbolic Tag Name> |
DATE |
DATE |
LONG |
0 to 65378 (days) |
|
<Symbolic Tag Name> |
TIME_OF_DAY (TOD) |
TIME_OF_DAY (TOD) |
ULONG |
0 to 86399999 (milliseconds) |
|
<Symbolic Tag Name> |
DATE_AND_TIME |
N/A |
STRING |
1990-01-01-00:00:00.000 to 2089-12-31-23:59:59.999 |
|
<Symbolic Tag Name> |
LTIME |
N/A |
STRING |
-9223372036854775808 to +9223372036854775807 (nanoseconds) |
|
<Symbolic Tag Name> |
LTOD (LTIME_OF_DAY) |
N/A |
STRING |
0 to 8639999999999 (nanoseconds) |
|
<Symbolic Tag Name> |
LDT |
N/A |
STRING |
0 to 9254908036854775808 (nanoseconds) |
When configuring tags to access PLC arrays and structures, a separate tag needs to be created for each array or structure element.
The driver supports conversions between S7-PLC data types and Plant SCADA data types. When a configured tag data type cannot be converted into PLC data type, the driver marks that tag with quality Bad, Configuration Error.
The following table shows supported conversions between Plant SCADA and S7-PLC data types.
|
Plant SCADA Data Type |
S7-PLC Data Type |
|---|---|
|
DIGITAL |
BOOL |
|
INT, UINT |
BYTE, WORD, SINT, USINT, INT,UINT |
|
LONG, UINT |
BYTE, WORD, DWORD, SINT, USINT, INT,UINT, DINT, UDINT |
|
REAL |
REAL |
|
STRING |
All S7-PLC data types supported by the driver, except for BYTE, USINT, WORD, UINT, DATE |