in Table 1-1. Note that these features aresomewhat generalized network speed is shownas 9.6kbit/s (lower limit) to 12,000kbit/s (upperlimit), although the network speed may varydepending on the medium or technology used.For example, MBP-IS, the medium used forPROFIBUS PA, operates at a single baud rate of31.25kbit/s. An interesting feature of PROFIBUS isthat the protocol is the same no matter what transmissionmedium or technology is used. Thus, PROFIBUSDP (utilizing RS-485 copper, fiber optics,infrared, and so on) and PROFIBUS PA (utilizingMBP-IS), use the same protocol and thedevices can exchange cyclic I/O data with a standardDP master.FMS will not be covered in this guide since itsprimary function of peer-to-peer (master-master)communication has been mostly replaced inrecent years by Ethernet-based protocols.2 BASICS OF PROFIBUS OPERATIONTable 1-1 PROFIBUS FeaturesPROFIBUS is an open, vendor-independent protocolthat became part of the international standardIEC 61158 in 2000. Though the protocol ismature, it certainly is not static! Over time, ithas been extended into new application areas byworking groups of employees from companiesthat have similar products and target applicationareas. These extensions have always been developedunder the requirement that they ensurebackward compatibility. This pocket guide isnot the place to discuss the details of theseextensions and will concentrate primarily on thebasic DPV0 operations; however, Figure 1-1 listsBASICS OF PROFIBUS OPERATION 3the extensions that have been standardized inthe past few years.Figure 1-1 PROFIBUS DP ExtensionsAs Figure 1-1 shows, DPV0 is the foundation forPROFIBUS and was the first version after FMS.DPV0 came from optimizations to FMS, theoriginal PROFIBUS protocol, to support fastI/O data exchange. PROFIBUS DPV1 addedextensions that allowed run-time reading/writingof parameters for more sophisticated devicessuch as intelligent drives, for example, andPROFIBUS PA field instruments, such as valvepositioners, pressure transmitters, and so on.DPV2 added extensions primarily so thatmotion-control applications can be performed4 BASICS OF PROFIBUS OPERATIONdirectly across PROFIBUS rather than requiringa secondary motion-control bus.This first chapter will give you a brief overviewof the cyclic I/O data exchange (DPV0) operationof a PROFIBUS network. It will not dealwith how you set up the network to operate.Chapter 2 will discuss that topic. Here, we willcover four basic aspects of a PROFIBUS DP network: Master/Slave Concept: A general overviewof device interactions. Device and System Startup: Just how doesthe master get all those devices and the systeminto operational mode for control? Cyclic I/O Data Exchange: What the networknormally does when it is hummingalong at up to 12,000kbit/s. Device Diagnostic Reporting: What diagnosticscan a device report and what does adevice do when it detects a diagnostic condition,for example, a wire break on an outputpoint?