2 PROFINET IO in SIPROTEC
2.9 Executing Switching Operations via PROFINET IO
50 SIPROTEC 4, Communication Module PROFINET IO, Communication Profile
C53000-L1840-C360-1, Edition 08.2012
2.9.2 Recommended Transmission of Commands via PROFINET IO
Outputs or internal tags are only set via PROFINET IO in the SIPROTEC device if a corresponding value
change is detected at the associated bit positions of the IO module in the PROFINET IO output telegram (trig-
gered by change; see description on Continuous Outputs and Pulse Outputs in Chapter 2.9.1).
If the bit combination for a command changes and the bit value for ON or OFF is still transmitted (statically) in
the cyclic output telegram, this has no consequences in the SIPROTEC device while communication is running.
A statically set bit combination for ON or OFF may cause undesirable command executions when communica-
tion is restored in the event of communication interruptions (see Chapter 2.10) or STOP of the PLC (see
Chapter 3.3.2.1) or when the PLC switches from STOP to RUN.
Siemens therefore recommends transmitting switching operations or set taggings in SIPROTEC devices via
PROFINET IO by using a pulse over the bus:
• Idle state ("00") → ON ("10") → idle state ("00") for switching on
• Idle state ("00") → OFF ("01") → idle state ("00") for switching off
The pulse duration (period during which the bit combinations for ON or OFF apply) should be at least 3 times
the set cycle time of the IO device (reference value at least approx. 100 ms).
NOTE
A value change at the associated bit position in the PROFINET IO telegram triggers a command processing
operation in the SIPROTEC device. However, this does not mean that the associated output or the associated
tagging actually takes the set point value. For example, the setting of an output caused by interlocking can be
rejected. The feedback of a switching device or the tagging should be read back for monitoring purposes.
com_profinet-io_profile_us.book Page 50 Friday, August 17, 2012 1:40 PM
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