Siemens SINUMERIK 840Di Function Manual page 964

Detailed description
2.7 Structure and functions of the basic program
Read/write NC variables
NCK variables can be read with FB GET while values can be entered in NCK variables with
FB PUT. The NCK variables are addressed via identifiers at inputs Addr1 to Addr8. The
identifiers (symbols) point to address data, which must be stored in a global DB. To allow
generation of this DB, PC software is supplied with the basic program with which the
required variables can be selected from a table, which is also supplied. The selected
variables are first collected in a second, projectrelated list. Command Generate DB creates a
*.AWL file, which must be linked to the program file for the machine concerned and compiled
together with the machine program.
1 to 8 values can be read or written with a read or write job. If necessary, the values are
converted (e.g., NCK floating point values (64 bits) are converted to PLC format (32 bits with
24-bit mantissa and 8bit exponent) and vice versa). A loss of accuracy results from the
conversion from 64 bits to 32bit REAL. The maximum precision of 32bit REAL numbers is
approximately 10 to the power of 7.
2.7.7 Symbolic programming of user program with interface DB
General
Note
With basic program SW 3.2 and higher, files NST_UDT.STL and TM_UDT.AWL are stored
on the basic program diskette supplied with the system.
The compiled UDT blocks from these two files are stored in the CPU program of the basic
program.
A UDT is a data type defined by the user that can, for example, be assigned to a data block
generated in the CPU.
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Power Line Basic PLC Program (P3)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0