Siemens SINUMERIK 840D sl Function Manual page 169

B3: Several operator panels connected to several NCUs, distributed systems - only 840D sl
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.
Writing
A link variable is written with main-run synchronism.
Reading
A preprocessing stop is triggered when a link variable is read.
Checks
The following checks are performed for the link variables and link variables memory:
● Observance of the value range limits
● Access to format limit
● Observance of defined memory area in link variables memory
The user/machine manufacturer is solely responsible for preventing the following errors:
● Accessing with incorrect data format
● Accessing the wrong address (index i)
Extended Functions
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
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
2.8 Link communication
Value range
0 to 255
-32,768 to 32,767
to 1.8*10 )
-308 +308
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