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32 Function Description WAGO-I/O-SYSTEM 750750-652 Serial Interface RS-232 / RS-485Manual1.2.0Pos : 69 /All e Seri en (Allgemei ne Module)/Ü berschriften für alle Serien/F unktions bes chr eibung - Ü berschrift 1 @ 4\mod_1239025975389_21.doc x @ 30003 @ 1 @ 15 Function DescriptionPos : 70.1 /All e Seri en ( Allgemei ne Module)/Ü bers chriften für alle SerienBetriebs arten für seriell e Ü ber tragung - Ü bersc hrift 2 @ 14\mod_1362750880945_21.doc x @ 114079 @ 2 @ 15.1 Operating Modes for Serial TransmissionPos : 70.2 /Serie 750 (WAGO-I/O-SYST EM)/F unktions beschr eibungFunkti ons besc hreibung 750-0652 - Betriebs arten für s eriell e Ü bertr agung @ 14\mod_1363001336668_21.doc x @ 114123 @ 34343444333 @ 1In denIn the operating modes for serial transmission, the I/O module allowscommunication with serial devices via RS-232, RS-485, RS-422 or DMX.The I/O module operates in these modes as a link between one of thesestandardized interfaces to the one side and the application or controller to theother side.Data transmission between the I/O module and serial devices is determined by therespective interface parameters, e.g. baud rate.Data transmission between the application and I/O module is controlled by thecontrol and status bytes.5.1.1 Transmit DataIf data is transmitted via the I/O module to an RS-232, RS-485, RS-422 interfaceor in DMX mode, the application writes to the data bytes of the process image(output) per each part of the data. The application modifies the control bytes, sothat they signal to the I/O module that new data has arrived. The I/O modulereceives the data sent to the output buffer and modifies the status bytes. Based onthese modified status bytes, the application can again recognize that the datatransfer was successful. Only when this feedback is present can the applicationtransmit the next part of the data.The data transmission rates between the application and I/O module and betweenthe I/O module and serial interface are normally not identical.If data transmission between the application and I/O module is faster thanbetween the I/O module and serial interface, the output buffer in the I/O modulefills up faster than it clears. If the application transmits continuously, the outputbuffer queue even rises when data is continuously transmitted on the serialinterface. If the output buffer is full, the application has to wait for space to beavailable in the output buffer by transmitting to the serial interface.If data transmission between application and I/O module is slower than betweenI/O module and serial interface, the output buffer in the I/O module fills up fasterthan it clears. Transmission of data on the serial interface is repeatedly interruptedeven if the application continuously transmits.5.1.1.1 Continuous TransmissionThe I/O module can be set either to transmit data in the output buffer to the serialinterface immediately or to start the transmission process only after released bythe application. The latter is useful when data has to be transmitted on the serialinterface according to time criteria, but data transmission between the applicationand I/O module is slower than between the I/O module and serial interface. |
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