GE PACSystems RXi User Manual

Chapter 10. PROFINET IO-Controller Operation208 PACSystems* RXi Distributed IO Controller User Manual GFK-2816F10.3 I/O ScanningIn the PACSystems RXi PROFINET network, multiple I/O cycles run asynchronously andindependently. The example below illustrates typical cycles in a system with an RXiController and VersaMax PNS modules used as IO-Devices. Cycles may be different forother GE Intelligent Platforms scanners and third-party devices.CPUPNCPSPNSDI PSPNSDIPROFINET IOPROFINET IOProduction CycleRXi CPU SweepPROFINETIO-Device Scan PROFINET IO-Device Scan: in this example, each VersaMax PNS scans all themodules in its node as quickly as possible. The PNS stores the modules’ input datainto its internal memory. On each PNS output scan, the Scanner writes the outputdata from its internal memory to the modules in its node. PROFINET IO Production Cycle: each PNC and each IO-Device publishes datafrom its internal memory onto the network at each scheduled PROFINET productioncycle. The PNC publishes output data received from the RXi CPU to each IO-Device,and the IO-Device publishes input data from its memory to the PNC.Note: Production cycles between IO-Controllers and IO-Devices are notsynchronized, each publishes at its configured update rate independently. RXi CPU Sweep: the sweep includes both an input scan and an output scan. TheCPU input scan retrieves the current input data from the PNC. This input data is thenavailable for use by the application logic. After the logic solution, the CPU outputscan writes the outputs to the PNC. 3rd party devices: The conveyance of I/O data between an I/O module and thePROFINET IO network is device dependent. Third party manufacturer documentationshould be referred to for specifics for a particular device.