                                                                                  | |
Contents
| 
WAGO-I/O-SYSTEM 750 Function Description 33750-652 Serial Interface RS-232 / RS-485Manual1.2.0If continuous transmission is activated, the I/O module evaluates the bit SC incontrol byte 0. Only when SC takes the value 1 does the I/O module transmit thedata contained in the output buffer to the serial interface. The application can setSC to 0 to prompt the I/O module to accumulate data in the output buffer.5.1.2 Receive DataIf the I/O module receives data via an RS-232, RS-485 or RS-422 interface, thedata is written to the input buffer of the I/O module. The I/O module transfers datato the application consecutively long as there is data in the input buffer. The I/Omodule writes the respective part of the data to the data bytes of the processimage. The I/O module modifies the status bytes. Based on these modified statusbytes, the application can recognize that new data has been received, which it canthen evaluate. The application modifies the control bytes, so that they signal to theI/O module that the data transfer was successful. Only when this feedback ispresent can the I/O module transmit the next part of the data received.5.1.2.1 Continuous ReceiptIf there is data in the input buffer, the I/O module can be set either to begintransmitting data to the application immediately or to wait to receive additionaldata.If the I/O module begins to transmit data to the application immediately, only partof a contiguous message may have been received by that point. Whether amessage has been transmitted on the serial interface according to time criteria isthen no longer evident for the application.Example: A serial device transmits 20 bytes. After the I/O module has received1 byte, it begins to transmit the date to the application. The I/O module transmitsthe remaining 19 bytes received in the meantime only after the application hasconfirmed receipt of the first byte.If continuous receipt is activated, the I/O module begins transmitting data to theapplication only if no additional data has been received on the serial interface fora specific period of time. In the example above, the I/O module would only starttransmitting data to the application when all 20 bytes have been received.The time period after which the I/O module starts data transmission can bedefined using the "Continuous Receive Timeout" parameter. Because the durationof the transfer of any amount of data depends on the baud rate setting, number ofdata and stop bits and the parity, an absolute time specification is not feasible.Therefore, the time required to transmit exactly one character to the serialinterface in the current interface parameter setting is used as the unit ofmeasurement. |
Related manuals for WAGO 750 Series
This manual is suitable for:
manualsdatabase
Your AI-powered manual search engine