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Overview of S7 protocol

The following image shows the data source input window for the S7 protocol:

Overview of S7 protocol

You can choose between automatic and manual connection type.

  • Automatic: This mode tries to find slot and rack number automatically.
  • Manual: In this mode you can enter the rack and slot number manually.

For S7 connection type the PG type-programmer-type-connection is used thus you will not be able to make use of PG connection.

Note

Symbolic access

This solution does not allow full symbolic access.

Requirements for S7-1200 and S7-1500

  • Put/Get communication must be permitted (can be found e.g. S7-1500 -> Properties -> Protection & Security -> Connection mechanisms).
  • The “Optimized block access” of the data blocks that you want to read must be deactivated (can be found in the data block properties).

Address format examples

Detailed examples:

Example address format DB15.DBX6.3:

DB15.DBX6.3

Area indicator Data type Offset address
DB15 - DB X 6 - 3
Datablock address Separator Datablock Bool Offset Byte Separator Offset Bit
Reads 3rd bit of byte 6 of datablock 15

Example address format IW10:

IW10

Area indicator Data type Offset address
I W 10
Process Input Word Offset Byte
Reads a word of input starting from offset 10

Overview

If you want to read data out of other areas, please replace “DB15.DB“ from the examples with the area indicator from the list below:

Attention: only certain address examples work with Inputs and Outputs (see²⁾).

S7 MindSphere
Data type Length/unsigned/signed Data type (length) Address example Description
Bool 1 bit BOOLEAN (1 bit) DB15.DBX6.3²⁾ Reads 3rd bit of byte
6 of datablock 15
Byte 1 byte / unsigned INT (4 bytes) LONG DB15.DBB4²⁾ Reads an unsigned byte
USInt (8 bytes) DOUBLE DB15.DBBYTE4 starting from offset 4
*(8 bytes)*¹⁾ out of datablock 15.
SInt 1 byte / signed
Char 1 byte / signed DB15.DBCHAR6 Reads a char starting
from offset 6 of
datablock 15.
Word 2 bytes / unsigned DB15.DBW10²⁾ Reads an unsigned word
UInt DB15.DBWORD10 starting from offset 10
of datablock 15.
Int 2 bytes / signed DB15.DBINT12 Reads a signed integer
starting from offset 12
out of datablock 15.
DINT 4 bytes / signed DB15.DBDINT28 Reads a signed double
integer starting from
offset 28 of datablock 15.
DWord 4 bytes / unsigned LONG (8 bytes) DB15.DBDW24²⁾ Reads an unsigned double
UDInt DOUBLE *(8 bytes)*¹⁾ DB15.DBDWORD24 word starting from offset
24 of datablock 15.
Real 4 bytes / signed DOUBLE (8 bytes) DB15.DBD32²⁾ Reads a floating-point
DB15.DBREAL32 number starting from
offset 32 of datablock 15.
String Length of variable, STRING DB15.DBSTRING10 The maximum string length
max. 254 bytes (max. 254 bytes) (Byte10) is read first.
Then the number of bytes
that Byte10 indicates are
number read. After that
the of bytes that Byte11
indicates are extracted
from the byte array that
is the result of second
read operation.
For example:
- (Byte10)- 30
- (Byte11)-4
- (Byte12-Byte15)-TEST
First read result: 30
Second read result: 4TEST
We will extract TEST from
the second read result by
considering Byte11's value.
String Min. 100 bytes , DB15.DBSTRING10,100 Reads 100 bytes of string
max. 254 bytes starting from offset 10.

¹⁾ When DOUBLE is used for integers, they are converted to a floating-point number.

²⁾ For the areas Inputs and Outputs only certain address examples work.

Note

Signed values

If you want to read a signed value, you have to use the respective signed datablock.

Example:

DB1831.DBW508 is unsigned. You can use DB1831.DBINT508 instead.

Area Types

S7 datapoint addresses must contain an area type.

Area indicator Area types Description
C Counter Reads Counter value of hardware.
DB Datablock Reads datablock value from hardware.
DI Instance Data Reads data directly from hardware.
I Process Input Reads Input value of Process image.
M Memory Reads Memory value of hardware.
PI Peripheral Input Reads Input value directly from hardware.
PQ Peripheral Output Reads Output value directly from hardware.
Q Process Output Reads Input value of Process image.
T Timer Reads Timer value of hardware.

Area Number

S7 datapoint addresses must contain area number.

E.g.: DB10 (10. datablock)

Data Types

The following table shows the MindSphere data types:

MindSphere data types:

Data type Length Date range: From Data range: To
BOOLEAN 1 bit True False
INT 4 bytes −2147483648 2147483647
LONG 8 bytes −9223372036854775808 9223372036854775807
DOUBLE 8 bytes -9.9999999999999999999999999999999999999E+125 9.9999999999999999999999999999999999999E+125
STRING 1-255 bytes

The following table shows the S7 data types:

S7 data types:

Data type Length Date range: From Data range: To
Bool 1 bit True False
Byte (unsigned) 1 byte 0 255
Word (unsigned) 2 bytes 0 65.535
DWord (unsigned) 4 bytes 0 4294967295
Char (signed) 1 byte −128 127
Int (signed) 2 bytes −32768 32767
DINT (signed) 4 bytes −2147483648 2147483647
Real 4 bytes ±1,18e-38 ±3.40e+38
String 1- 254 bytes

Offset

Variable types must have an offset. Offset is the starting byte number.

E.g. DW4 (a double word starting from byte 4)

String

Data type Length in bytes Format
STRING[n] or STRING n+2 ASCII character of any length. n specifies the length of the character string. A maximum length of 254 characters is permitted. If no length is specified, the default setting is 254 characters.
Data type Examples of format used
STRING[2] 'AB'
STRING[55] 'The character string can consist of up to 55 characters'

Note

You must enclose your character string in single quotation marks.

The following example shows the byte order when specifying the datatype STRING[4] with the output value 'AB'.

Datatype string

* Tod

TIME_OF_DAY (Time) 32 Time is in steps of 1 ms TOD#0.0.0.0 to TOD#23:59:59.999 L TOD#1:10:3.3
L TIME_OF_DAY#1:10:3.3

* Time

Returns milliseconds.

Format:

The DT (DATE_AND_TIME) datatype saves the information on date and time of day in BCD format.

The following table shows the properties of datatype DT:

Length (bytes) Format Range of values Example of value input
8 Date and time (year-month-day)

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Last update: May 19, 2022