11.03 7 Configuring example
7.6 SI I/Os using fail-safe modules connected to PROFIBUS DP
© Siemens AG 2003 All Rights Reserved
SINUMERIK 840D/SIMODRIVE 611 digital SINUMERIK Safety Integrated (FBSI) - Edition 11.03
7-441
7.6.8 Modified limitations with PROFIsafe
When compared to connecting the SPL I/O with two separate hardware
I/O branches (NCK and PLC I/Os), when connected via SPL I/Os using one
safety-relevant bus (PROFIsafe) results in some modified limitations when it
comes to configuring and programming:
• Error in the PROFIsafe input devices (e.g. input signals that differ from one
another) cause the associated SPL-SGEs to be cleared. This initiates a
STOP D/E .
• The external SPL input signals in the DB18 interface for the $A_INSEP
variables are transferred within the system, i.e. programming is no longer
necessary in the user program. The PROFIsafe input I/Os now only
transfer one signal state to the master for both SPL channels, i.e. data
crosswise comparison is no longer performed in the control for the
$A_INSE(P) variables.
• The external SPL output signals of the DB18 interface ($A_OUTSEP
variables) are transferred within the system to the relevant PROFIsafe
output modules. Since only one signal state is transferred via PROFIsafe, it
is no longer possible to temporarily output a signal state for the PLC output
that is different from the NCK output (as implemented previously for
exceptional cases). There is now no
PLC branch and no NCK branch for a
safe PROFIsafe output that has a two-channel structure.
• If may be necessary to use single-channel signals (signals that are present
only in the PLC or only in the NCK) to change over external SPL outputs
(e.g. brake control). This fact means that these single-channel signals must
also be made available to the other program channel to align the logic and
program synchronously. Direct communications between the NCK and
PLC-SPL via DB18 is a good way to achieve this.
•
In each PROFIsafe cycle, the PROFIsafe layer generates a PROFIsafe
telegram with the logically AND'ed SPL output data as F net (useful) data.
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