Siemens SINUMERIK 840D sl Function Manual page 168
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Several Operator Panels on Several NCUs, Distributed Systems (B3)
Link communication
Properties of the link variables memory
Assigning parameters for the memory size
The size of the link variables memory in bytes is set by means of the following machine data:
MD18700 $MN_MM_SIZEOF_LINKVAR_DATA (size of the NCU link variables memory)
The setting for the size of the link variables memory should be identical for all NCUs involved
in the link grouping. If the memory sizes are different, the largest value assigned is used.
Initialization
After an NCU is powered up, the link variables memory is initialized with 0.
Structure
From the point of view of the system, the link variables memory is an unstructured memory
area that is available for link communication purposes. The link variables memory is
structured by the user/machine manufacturer alone. Depending on how the data structure is
defined, the link variables memory is accessed by means of data format-specific link
variables.
System-wide alignment
Once a link variables memory has been written to, the changes that have been made to the
data are transferred to the link variables memories of all other NCUs involved in the link
grouping. The link variables memories are usually updated by means of link communication
within two interpolation cycles.
Properties of the link variables
The link variables memory is accessed via the following data format-specific link variables:
Data type
Name
1)
UINT
$A_DLB[ i ]
INT
$A_DLW[ i ]
INT
$A_DLD[ i ]
REAL
$A_DLR[ i ]
1) Data type of link variables when used in part program/cycle
2) Data format of link variables or number of bytes addressed by the link variables in the link variables memory
3) The following must be noted for index i:
Index i is a byte index that relates to the beginning of the link variables memory.
•
The index must be selected so that the bytes addressed in the link variables memory are located on a data format limit
•
⇒ index i = n * bytes, where n = 0, 1, 2, etc.
–
$A_DLB[i]: i = 0, 1, 2, etc.
–
$A_DLW[i]: i = 0, 2, 4, etc.
–
$A_DLD[i]: i = 0, 4, 8, etc.
–
$A_DLR[i]: i = 0, 8, 16, etc.
168
Data format
Bytes
2)
BYTE
1
WORD
2
DWORD
4
REAL
8
Index i
2)
3)
i = n * 1
i = n * 2
i = n * 4
-2,147,483,648 to 2,147,483,647
i = n * 8
±(2.2*10
Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Value range
0 to 255
-32,768 to 32,767
to 1.8*10
)
-308
+308
Extended Functions
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