The communication channels to S7 or AtS7 PLCs can be defined here.
A communication channel is referenced by its name. (normally the name of the relevant PLC)
The name of the communication channel is relevant for the variable names.
See also:
| • | Driver settings: DrvParam worksheet |
| • | Host parameters: Rs7Hosts worksheet |
Variable addressing
As EPAM always works with symbolic variables, the addresses of the symbols must be entered in the UserVar worksheet in the Address column.
Supported address notation
Data block
Data type |
Abbreviated form |
S7 notation |
BYTE |
DB<x>.<y> |
DB<x>.DBB<y> |
WORD |
DB<x>.DBW<y> |
|
DWORD |
DB<x>.DBD<y> |
|
BOOL |
DB<x>.DBX<y>.<z> |
Markers
Data type |
Abbreviated form |
S7 notation |
BYTE |
MB<x> |
|
WORD |
MW<x> |
|
DWORD |
MD<x> |
|
BOOL |
M<x>.<y> |
Restrictions and special features
Byte order problem
S7-compatible PLCs use the Big-Endian format, whilst EPAM (x86) on the other hand uses the Little-Endian format.
The communication driver makes the necessary conversion according to the following schema.
Conversion to EPAM type
If a variable consists of a byte address, the VarType is used for the conversion.
Example.
Address |
VarType |
Conversion |
DB10.DBB8 |
WORD |
Read 2 bytes, swap bytes |
Conversion according to address type
If a variable does not consist of a byte address, but of a WORD address, for example, the type of the
address is used for the conversion.
Example.
Address |
VarType |
Conversion |
DB10.DBW8 |
WORD |
Read 2 bytes, swap bytes |
STRING
In the S7, the first two bytes of a string variable contain the maximum and effective length of the string. The maximum length must match the data type. The default length for STRING is 80.
Data types
The following data types correspond:
EPAM |
S7 |
Comment |
BOOL |
BOOL (Bit) / BYTE |
An EPAM BOOL can be defined in the PLC as BOOL as well as BYTE. |
BYTE/USINT |
BYTE |
|
SINT |
BYTE |
|
WORD/UINT |
WORD |
|
INT |
INT |
|
DINT |
DWORD |
|
DWORD |
DWORD |
|
REAL |
REAL |
|
STRING |
STRING |
|
DT |
DT |
The DT type of EPAM does not recognize [ms] so that the conversion loses accuracy |
TIME |
TIME |
|