Safe Software Relay - Siemens SINUMERIK 840D sl Function Manual

Connecting Sensors/Actuators
7.3 Safe programmable logic (SPL)
These instructions simulate the output interfaces of the NCK–SPL and therefore
"short–circuit" the crosswise data comparison.
Warning
!
The logic used in this phase has a single channel structure and is therefore not
safe!
The described minimum NCK–SPL must be replaced by a full NCK–SPL without
any access to $A_INSIP(D), ..., $A_MARKERSIP(D) when the PLC side is
completed!
Additional diagnostic support:
S $A_STATSID: A value not equal to 0 means that an error has occurred in the
crosswise data comparison. The error numbers are selected in the same way
as on the PLC side (see Chapter 7.3.11).
S $A_CMDSI[n]: n=1: 10x change timer value for long forced checking procedure
pulses and/or single–channel test stop logic.
S $A_LEVELSID: Indicates how many signals have different signal levels on the
NCK and PLC sides that can be presently detected.
S In addition, other NC variables or free R parameters can be written to monitor
internal states of the SPL.
The following applies to all system variables of the NCK–SPL outputs:
They can be written from and read back to the SPL program.
7.3.8

Safe software relay

The standard SPL block "safety software relay" is designed to meet the require-
ments of an Emergency Stop function with safe programmable logic. However, it
can also be used to implement other similar safety functions, e.g. to control a pro-
tective door.
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SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) – 05.2008 Edition
© Siemens AG 2008 All Rights Reserved
05.08