Detailed description
2.2 Functions
Basic logic functions: Various NC/PLC interface signals and functions (A2)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
35
Access from PLC
The PLC uses function calls (FC) to access the memory. These FCs ensure that data are
read and written in the DPR immediately, i.e., not just at the beginning of the PLC cycle. FCs
receive data type information and the position offset as parameters.
3/&'$7$ $B'%'>@
&$//)&
3/&
1&
'DWDW\SH'ZRUGE\WHV
3RVLWLRQRIIVHW[
Figure 2-9
Communications buffer (DPR) for NC/PLC communication
Supplementary conditions
•
The user's programming engineer (NCK and PLC) is responsible for organizing the DPR
memory area. No checks are made for inconsistencies in the configuration.
•
A total of 1024 bytes are available in the input and output directions.
•
Singlebit operations are not supported and must be linked back to byte operations by the
user (programming engineer).
•
Since the contents of variables are manipulated directly in the communications buffer, the
user must remember that intermediate changes in values occur as a result of multiple
access operations where a variable is evaluated several times or when variables are
linked (i.e., it may be necessary to store values temporarily in local variables or R
parameters or to set up a semaphore).
•
The user's programming engineer is responsible for coordinating access operations to the
communications buffer from different channels.
•
Data consistency can be guaranteed only for access operations up to 16 bits (byte and
word). The user's programming engineer is responsible for ensuring consistent
transmission of 32bit variables (double and real). A simple semaphore mechanism is
provided in the PLC for this purpose.
•
The PLC stores data in 'Little Endian' format in the DPR.
•
Values transferred with $A_DBR are subject to data conversion and hence to loss of
accuracy. The data format for floatingpoint numbers is DOUBLE (64 bits) on the NCK, but
only FLOAT (32 bits) on the PLC. The format used for storage in the dualport RAM is
FLOAT. Conversion takes place respectively before/after storage in the dualport RAM.
Summary of Contents for SINUMERIK 840D sl
Page 282: ...Index Basic logic functions Acceleration B2 64 Function Manual 11 2006 6FC5397 0BP10 2BA0 ...
Page 388: ...Basic logic functions Travel to fixed stop F1 Function Manual 11 2006 6FC5397 0BP10 2BA0 52 ...
Page 962: ...Index Basic logic functions Emergency Stop N2 20 Function Manual 11 2006 6FC5397 0BP10 2BA0 ...
Page 1704: ...Constraints Basic logic functions Spindles S1 94 Function Manual 11 2006 6FC5397 0BP10 2BA0 ...
Page 1716: ...Index Basic logic functions Spindles S1 106 Function Manual 11 2006 6FC5397 0BP10 2BA0 ...
Page 1996: ...Index Basic logic functions Tool Offset W1 208 Function Manual 11 2006 6FC5397 0BP10 2BA0 ...
Page 2150: ...Table of contents Basic logic functions Appendix 4 Function Manual 11 2006 6FC5397 0BP10 2BA0 ...
Page 2184: ...Glossary Basic logic functions Appendix 38 Function Manual 11 2006 6FC5397 0BP10 2BA0 ...