System Data - Siemens SINUMERIK 840D sl Programming Manual

Work preparation
3.1 Flexible NC programming
3.1.1.1

System data

The system data contain the variables that are predefined in the system and enable access to
the current parameter settings of the control, as well as to machine, control, and process states,
in NC programs and cycles.
Preprocessing variables
Preprocessing variables are system data that are read and written during preprocessing, in
other words, at the instant at which the block containing the variable is interpreted.
Preprocessing variables do not trigger preprocessing stops.
Main run variables
Main run variables are system data that are read and written during the main run, in other
words, at the instant at which the block containing the variable is executed. The following are
main run variables:
● Variables that can be programmed in synchronized actions (read/write)
● Variables that can be programmed in the NC program and trigger preprocessing stops (read/
write)
● Variables that can be programmed in the NC program and whose value is calculated during
preprocessing but not written until the main run (main run synchronized: write only)
Prefix system
To distinguish system data from other data, their names are usually preceded by a prefix
comprising the $ sign followed by one or two letters and an underscore.
$ + 1. Letter
Preprocessing data (system data that are read/written during preprocessing)
$M
$S
$T
$P
$C
$O
R
Main run data (system data that are read/written during the main run)
$$M
$$S
$A
$V
390
Meaning: Data type
Machine data
1)
Setting data, protection areas
Tool management data
Programmed values
Cycle variables of ISO envelope cycles
Option data
R-parameters (arithmetic parameters)
Machine data
1)
Setting data
1)
Current main run data
Position controller data
1)
2)
Programming Manual, 12/2019, 6FC5398-2EP40-0BA0
NC programming