Service & Support. Mechanisms of CP to Send and Receive Data. "Telecontrol" mode for communication between S station and control center

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1 Cover Mechanisms of CP4-7 to Send and Receive Data "Telecontrol" mode for communication between S7-00 station and control center FAQ April 0 Service & Support Answers for industry.

2 Question This entry is from the Siemens Industry Online Support. The general terms of use ( apply. Clicking the link below directly displays the download page of this document. Caution The functions and solutions described in this article confine themselves predominantly to the realization of the automation task. Furthermore, please take into account that corresponding protective measures have to be taken in the context of Industrial Security when connecting your equipment to other parts of the plant, the enterprise network or the internet. Further information can be found in Entry ID Question Which mechanisms does the CP4-7 use in "Telecontrol" mode to send and receive data? Answer The instructions and notes listed in this document provide a detailed answer to this question. V.0, Item ID:

3 Table of Contents Table of Contents Introduction... 4 Sending and Receiving Data in "Telecontrol" Mode The S7-00 Transfers Data to the Central Unit (TC_SEND) Immediate transfer of the process data to the telecontrol server Transfer of the process data by request of the telecontrol server The Central Unit Reads the Data from the S7-00 Station (read) The Central Unit Transfers Data to the S7-00 Station (TC_RECV and write)... 8 Data Buffering if Connection is Disconnected... 0 V.0, Item ID:

4 Introduction Introduction The CP4-7 is designed for industrial application. It supports telecontrol applications among others. Table - Telecontrol application Sending messages by SMS Communication with a central unit Cross communication between S7-00 stations over the GSM network Description The function is independent of the CP operating mode. Over the CP4-7 the CPU of a remote S7-00 station receives SMS messages from the GSM network or sends SMS messages to a configured mobile telephone or to an S7-00. The CP is configured in "Telecontrol" mode. Remote S7-00 stations communicate over the GSM network and the internet with a telecontrol server in the central unit. By way of the integrated OPC server function the telecontrol server communicates with a higher-level control system. Cross communication between remote stations with CP4-7 is done in different ways depending on the GSM service used and the CP operating mode: Indirect communication over a central unit ("Telecontrol" mode) In this configuration the connections between S7-00 stations and the telecontrol server are established in the central unit. The telecontrol server forwards the messages between the stations. Direct communication between stations ("GPRS direct" mode") The CP needs to have a fixed IP address assigned by the GSM network operator. "Telecontrol" operating mode The operating mode of the CP enables the GPRS station to exchange data with a telecontrol server. The telecontrol server is a PC connected to the internet with the "TELECONTROL SERVER BASIC" application. It is usually in the central unit and is for monitoring and controlling the remote GPRS stations. Below are possible communications partners of the GPRS station with CP4-7 in "Telecontrol" mode: A telecontrol server A central control system (over the OPC interface of the telecontrol server) An Engineering Station (for TeleService) Up to 5000 GPRS stations logged on to the telecontrol server with CP4-7 4 V.0, Item ID:

5 Introduction In "Telecontrol" mode you have the following options for transferring data: The S7-00 station transfers data to the central unit (TC_SEND). The central unit reads the data from the S7-00 station (read). The central unit transfers data to the S7-00 station (TC_RECV and write). The CP4 works with two process images for data exchange. It has a Send process image and a Receive process image. The Send process image (Process Image TX) is used as follows: When the TC_SEND instruction is called and processed in the S7-00 program. When the TELECONTROL SERVER BASIC sends a read job to the CP (read). The Receive process image (Process Image RX) is used as follows: When the TC_RECV instruction is called in the S7-00 program and data reception is enabled. When the TELECONTROL SERVER BASIC sends a write job to the CP (write). The maximum size of each process image is 048 bytes. Figure - PLC TC_SEND TC_SEND CP4 Process Image TX read write TELECONTROL SERVER BASIC TC_RECV TC_RECV Process Image RX # Notes The Send and Receive areas are to be separated on the CPU. V.0, Item ID:

6 Sending and Receiving Data in "Telecontrol" Mode Sending and Receiving Data in "Telecontrol" Mode This chapter describes in detail the possible processes for data transfer in "Telecontrol" mode.. The S7-00 Transfers Data to the Central Unit (TC_SEND).. Immediate transfer of the process data to the telecontrol server Requirements The OPC server is started in the central unit, which means an OPC client has established a connection to the OPC server. The "TC_CON" instruction has been executed successfully. RemoteWdcAddress is set to 0. Function Figure - shows a graphical overview of the processes when the S7-00 station transfers data to the central unit. Figure - PLC TC_SEND CP4-7 process image TX TELECONTROL SERVER BASIC and OPC client Table - Step Description The TC_SEND instruction sends n bytes of data to the CP. The CP saves the data in its Send process image and compares the data: If the process image has less than n bytes or is not yet available, the data is stored as a new process image. If the process image already has n bytes and no change is registered, the call is terminated and Step is skipped. If the process image already has more than n bytes, for example, due to previous TC_SEND calls with more than n bytes, only the first n bytes of the process image are overwritten. The process image (Process Image TX) is always transferred completely to the TELECONTROL SERVER BASIC. Notes The data that is sent can be from any random data block. It does not have to be DB. 6 V.0, Item ID:

7 Sending and Receiving Data in "Telecontrol" Mode.. Transfer of the process data by request of the telecontrol server Requirements The OPC server is started in the central unit, which means an OPC client has established a connection to the OPC server. The "TC_CON" instruction has been executed successfully. RemoteWdcAddress is set to 6#FEEDDADA. Function Figure - shows a graphical overview of the processes when the S7-00 station transfers data to the central unit only by request of the telecontrol server. This option is suited above all for cyclic data exchange triggered by the request of the telecontrol server ("cyclic communication") to provide data to the data archives at fixed intervals. Figure - PLC TC_SEND CP4-7 process image TX TELECONTROL SERVER BASIC and OPC client Table - Step Description The TC_SEND instruction sends n bytes of data to the CP. The CP saves the data in its Send process image. The CP overwrites the Send process image with new process data without comparing the new process data with the old process data. The process image (Process Image TX) is not transferred to the TELECONTROL SERVER BASIC. Only when the telecontrol server sends a request to the CP does the CP send the process image (Process Image TX) completely to the TELECONTROL SERVER BASIC. Notes The communications options with the telecontrol server described in sections.. and.. can also be implemented in parallel in the CP. For this you must call two different TC_CON instructions. V.0, Item ID:

8 Sending and Receiving Data in "Telecontrol" Mode. The Central Unit Reads the Data from the S7-00 Station (read) Requirements The "TC_CON" instruction has been executed successfully at least once. The process image (Process Image TX) is created the first time the TC_SEND instruction is called after startup. Function Figure - shows a graphical overview of the processes when the central unit reads data from the S7-00 station. Figure - PLC CP4-7 TELECONTROL SERVER BASIC and OPC client process image TX Table - Step Description The OPC server sends a read job to read x bytes starting at offset y. Since the process images is modeled in the CP as DB, the OPC server sends a read job of the items DB, DBx,y to the CP. The CP checks that the x bytes starting at offset y are in the process image. If yes, the specified x bytes are returned. If not, because the process image (Process Image TX) has less than x+y bytes, the read job is acknowledged negatively. The OPC client receives an error message in response to the read request.. The Central Unit Transfers Data to the S7-00 Station (TC_RECV and write) Function Figure -4 shows a graphical overview of the processes when the central unit transfers data to the S7-00 station. 8 V.0, Item ID:

9 Sending and Receiving Data in "Telecontrol" Mode Figure -4 PLC CP4-7 TELECONTROL SERVER BASIC and OPC client TC_RECV process image RX Table -4 Step Description The TELECONTROL SERVER BASIC writes x bytes starting at offset y. The CP saves the data in its Receive process image at the corresponding positions: If the process image (Process Image RX) has less than x+y bytes or is not yet available, the data is stored as a new process image. Data areas without a defined value are created with 0. The process image (Process Image RX) is always transferred completely to the TC_RECV. WARNING If the LEN parameter of the TC_RECV is less than the size of the process image, the status value at the TC_RECV is 6#80E0. Because a TC_RECV call always receives the complete process image regardless of the LEN parameter value, you should specify the maximum value 048 at the LEN parameter and the target area should also be just as large. V.0, Item ID:

10 Data Buffering if Connection is Disconnected Data Buffering if Connection is Disconnected If the telecontrol server is the connection partner, the following holds: If the wireless network fails, the CP stores up to 000 Send jobs with time stamp and sends them as soon as the connection is re-established. Notes The data is buffered only in "Telecontrol" mode. The data is not buffered: If the cross communication is in "Telecontrol" mode. If the communication is done in "GPRS direct" mode. 0 V.0, Item ID: