4-8
PACSystems* RX3i
PROFINET Controller Manual
– December 2011
GFK-2571A
4
I/O Scanning
In the PACSystems RX3i PROFINET network, multiple I/O cycles run asynchronously and
independently. The example below illustrates typical cycles in a system with an RX3i CPU with a
PNC module, and VersaMax PNS modules used as IO-Devices. Cycles may be different for third-
party devices.
P
S
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PROFINET IO
PROFINET IO
Production Cycle
RX3i CPU Sweep
PROFINET
IO-Device Scan
PROFINET IO-Device Scan
: in this example, each VersaMax PNS scans all the modules in
its node as quickly as possible. The PNS
stores the modules’ input data into its internal
memory. On each PNS output scan, the Scanner writes the output data from its internal
memory to the modules in its node.
3
rd
party devices:
The conveyance of I/O data between an I/O module and the PROFINET IO
network is device dependent. Third party manufacturer documentation should be referred to for
specifics for a particular device.
PROFINET IO Production Cycle
: each PNC in a CPU node and each IO-Device publishes
data from its internal memory onto the network at each scheduled PROFINET production
cycle (note: production cycles between IO-Controllers and IO-Devices are not synchronized,
each publishes at its configured update rate independently). The PNC publishes output data
received from the RX3i CPU to each IO-Device, and the IO-Device publishes input data from
its memory to the PNC.
RX3i CPU Sweep
: the RX3i CPU Sweep includes both an input scan and an output scan.
The CPU input scan retrieves the current input data being stored within the PNC module.
This input data is then available for use by the application logic. After the logic solution, the
CPU output scan writes the outputs to the PNC.