                                                                                                                                                                                                                                                  | |
Contents
|
44 • Fieldbus Controller 750-841Operating SystemWAGO-I/O-SYSTEM 750ETHERNET TCP/IP3.1.4 Operating System3.1.4.1 Start-upThe controller starts-up after switching on the supply voltage or after ahardware reset.NoteThe Operating Mode slide switch must not be in the bottom position duringstart-up!The PLC program in the flash memory is transferred to RAM.This is followed by the initialization of the system. The controller determinesthe I/O modules and the present configuration. The variables are set to 0,FALSE, or to an initial value given by the PLC program. The flags retain theirstatus . The "I/O" LED blinks red during this phase.Following a fault free start-up the controller changes over to "RUN" mode.The "I/O" LED lights up green.3.1.4.2 PLC CycleThe PLC cycle starts following a fault free start-up when the Operating ModeSwitch is in the top position or by a start command from theWAGO-I/O-PRO CAA. The controller starts a PLC cycle by first reading thefieldbus data, I/O modules, and time data. Next, the PLC program in RAM isprocessed (scanned). After the program is processed, the fieldbus data and I/Omodules are updated with new output data. System functions are thenpreformed (i.e., system diagnostics, communications, time calculations, etc).At this point, if a STOP command is not present, the cycle starts over againwith the reading of the fieldbus data, I/O modules, and time data.The change of the operating mode (STOP/RUN) is only made at the end of aPLC cycle.The cycle time is the time from the start of the PLC program to the next start.If a sizeable loop is programmed within a PLC program, the PLC cycle time isextended correspondingly.The inputs and outputs are not updated during the scanning of the PLCprogram. I/O updates only occur at the end of the PLC program scan. For thisreason, it is not possible to wait for a physical I/O change from within aprogram loop. |
Related manuals for WAGO 750 Series
This manual is suitable for:
manualsdatabase
Your AI-powered manual search engine