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

Data Description
8.4 System variables
$A_PLCSIIN[1...32] Single-channel direct communica-
tion between NCK and PLC-SPL.
Signals can be written by the PLC
and read by the NCK.
$A_PLCSIOUT[1...32] Single-channel direct communica-
tion between NCK and PLC-SPL.
Signals can be read by the PLC,
written and read by the NCK.
8.4.2

Description of the system variables

System variable $VA_IS
The safe actual value, used by SI, can be read and further processed by the NC
part program for every axis/spindle.
Example:
When an NC part program is started, Safety Integrated checks whether axis X
would move into the vicinity of shutdown limits as a result of the zero offsets when
a program is processed. The part program can be programmed as follows, for ex-
ample:
IF ($VA_IS[X] < 10000) GOTOF POS_OK
MESG ("Axis has nearly reached limit switch!")
POS_OK:
...
The variable can also be used in synchronous actions in order to reduce the over-
ride when the axis is nearly at the limit switch.
Difference between $VA_IS and $AA_IM
Both variable $VA_IS and variable $AA_IM can be used to read actual values.
8-332
SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) – 03.2006 Edition
[FALSE, BOOL x
TRUE]
[FALSE, BOOL x
TRUE]
; if the actual value is too
high,
; then the following mes-
sage,
; otherwise, continue here
© Siemens AG, 2006. All rights reserved
03.06
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