Siemens S7-300 - IO Controller Mode with S7-300; Programming

CP as PROFINET IO controller
6.2 IO controller mode with S7-300
Configuring and commissioning S7 CPs for Industrial Ethernet
Configuration Manual, 09/2013, C79000-G8976-C182-13
117
Mode of the CP in PROFINET IO with IRT communication - simultaneous operation as IO device and
IO controller
If you use the CP for IRT communication (Isochronous Real Time), remember the following
when you select the mode of the CP:
● You can configure the CP as IRT controller and RT device or as IRT device and RT
controller at the same time.
● It is not possible to operate the CP as IRT controller and IRT device at the same time.
6.2
IO controller mode with S7-300
6.2.1
Programming
Process data transfer with program blocks
To write and read process data, use the following program blocks in your user program:
● PNIO_SEND (FC11), send process data
● PNIO_RECV (FC12), receive process data
Optimized data transfer - response after failure of an IO device
In PROFINET IO controller mode, it is possible to optimize data transfer on the PROFINET
IO interface.
This optimization is achieved by calling the program blocks with a length (LEN parameter)
that it is shorter than the configured total length of the IO data on the PNIO line.
You can use this so that timecritical data is transferred in every CPU cycle whereas non
critical data is not transferred in every cycle.
Example:
You could, for example, transfer only the first data area (timecritical data) in every cycle and
the total length of the configured IO data in every second cycle. To do this, place the time-
critical data in the lower area (starting at IO address 0) during configuration.
● Response after failure of an IO device
If you do without transferring the total length of the configured IO data in certain cycles,
the following situation may arise:
– Following a device failure and hot restart, an IO device does not output any process
data.
Reason:
An IO device only outputs data again following a device failure after the IO controller
(here the CP) has transferred the entire output data area!