PROFISafe NEW PRODUCTS DEVELOPMENT KIT ... - Siemens

used in case of diagnostic situations. If control and safetydevices could be combined on a single bus, how would thesystem look? Let's take a look at figure 2.Figure 2 - How the system should lookdevices exchange data like they always do. The controllersends output data (up to 244 bytes) to a field device and thedevice answers with input data (up to 244 bytes). APROFISafe device does exactly the same.The enhancement is that the data section ispartly used for safety relevant information thatwill be evaluated in accordance with thePROFISafe profile implementation in thereceiving station. Figure 4 shows the datasection of a standard PROFIBUS telegram toa PROFISafe device.The F-I/O section is used to transfer the failsafeprocess data of the safety modules. TheControl Byte is used by the controller to sendcommands to the field device, e.g., to assigna new parameter set. In the response, theStatus Byte is used by the field device to signalevents, e.g., the expiration of watchdogWouldn't it be great if you could utilizePROFIBUS for both your standard automationtask AND for the safety related issues at thesame time? Wouldn't it be nice if you couldconnect safety devices like emergency pushbuttonsor light curtains to the same wire asHMI panels or drives? Wouldn't it be helpful tosave costs via the combination of standardand safety I/O modules in the same fielddevice? This is exactly what PROFISafe does- it makes a special or additional solution for safety-relatedissues unnecessary.How is it implemented?Because PROFISafe is defined as a profile within the socalledapplication layer level, the standard PROFIBUS communicationmechanisms are not affected. You continue touse the cable and components to install your network youused before. If you are a device manufacturer, you continueto use the same ASICs (the chip sets to migrate PROFIBUStechnology into your device) that you have used before.Figure 3 shows the implementation principle (the communicationlayers are not safety relevant). And how does thecommunication between safety devices work? PROFIBUSASICs, Links, Cables, ... - NOT safety relevantFunctions e.g. diagnostic - NOT safety relevantFigure 4 - PROFISafe Telegram (Data Unit)Parts of the failsafe communications systems, e.g. watchdog timers as deined in the profileSafety relevant, but not part of the profile, e.g. Safety I/OFigure 3 - PROFISafe and the 7 Layer Communication Modeltimers. The Sequence Number serves as a counter to monitorthe life of the controller and the communication link. TheCRC key is generated on both ends of the communicationlink and is used as a check sequence to validate the receivedfailsafe data.Figure 5 shows how PROFISafe works.1. The emergency button (connected to a failsafe input modulein the field device) is pushed.2. During the next communication cycle, the safety controller(e.g., a PLC that is able to handle the safety application andalso the standard automation task) sends output data to thefield device (including failsafe data according to thePROFISafe profile).3. The field device responds with input data(including failsafe data according to thePROFISafe profile).4. The safety application in the controller evaluatesthe relevant part of the data unit and initiatesthe necessary steps according to theprogram. In our example, load power needs tobe disabled via a failsafe output.5. With the next telegram, the information issent to the appropriate station as part of theoutput data.6. The motor stops.With PROFISafe, this safety scenario is availabletoday and the next enhancements arealready in preparation. Direct communication3