Description Of The System Variables - Siemens SINUMERIK 840D sl Function Manual

System variable
$A_PLCSIOUT[n] Single-channel direct communica‐
tion between NCK and PLC-SPL.
Signals can be read by the PLC,
written and read by the NCK.
$AC_SAFE_SYNA_ Free safety synchronized action el‐
MEM ements
$VA_SAFE_TYPE[a Information about the active safety
xis] operating mode of this axis
Note:
r → read, w → write
An implicit preliminary stop is generated
Only permitted in the commissioning phase
The number of these system variables depends on the option SI Basic, SI Comfort or SI High-Feature.
1)
SI Basic 4I / 4O
SI Comfort 64I / 64O
SI High-Feature 192I / 192O
9.7.2

Description of the system variables

System variable $VA_IS
The safe actual value, used by SI, can be read and further processed by the NC part program
for every axis/spindle.
Example:
When an NC part program is started, Safety Integrated checks whether axis X would move
into the vicinity of shutdown limits as a result of the zero offsets when a program is processed.
The part program can be programmed as follows, for example:
IF ($VA_IS[X] < 10000) GOTOF POS_OK
MESG ("Axis has nearly reached limit switch!")
POS_OK:
...
The variable can also be used in synchronized actions in order to reduce the override when
the axis is nearly at the limit switch.
Safety Integrated
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Meaning
n = 1,2, ... 96
[0, MAX_INT]
[0, 1, 2]
Value range Data type
BOOL
1)
INT
;if the actual value is too high,
;then message,
;otherwise, continue here
Data descriptions
9.7 System variable
Possible access for
Part Synchronized
program action
r w r w
x x
x x
x x
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