Background of PROFIBUS

PROFIBUS (Process Field Bus) was once a standard developed by Siemens for field bus communication in automation technology. Through the merger of more than 20 institutions and companies in 1987, there should be found a way to create a uniform standard for a bit-serial field bus.
The standardization of the field device interface should create the basis for the use of the fieldbus in the manufacturing, process and building automation later. Therefore a common and uniform technical concept, as well as a communication model was needed. So PROFIBUS was standardized in the international standard IEC 61158.
PROFIBUS is a multi-master system that enables the joint operation of multiple systems with decentralized peripheral equipment on one bus. The protocol architecture is based on recognized international standards – in this case, it is based on the OSI (Open System Interconnection) reference model, according to the ISO 7498 standard.
Each transmission layer handles precisely defined tasks. Layer 1 (Physical Layer) defines the transmission physics, Layer 2 (Data Link Layer) the bus access protocol and layer 7 (Application Layer) the application functions.
The fieldbus standard PROFIBUS has gradually expanded in recent years to ever new areas of application, the PROFIBUS DP is the most widely used variant.

Scheme: PROFIBUS Layer-Model in OSI Model

PROFIBUS Device Types

Master Devices:

The Master is a so-called “active participant”, which determines all the traffic on the bus. It is the only component that is authorized to access a resource without being asked and to send messages without an external request.

Slave Devices:

Slaves are in turn “passive participant”, which have no independent authorization to access the resource. They need to be prompted for a bus access directly from the Master.

PROFIBUS Protocol Versions

PROFIBUS DP (Decentralized Peripherals)

… for communication between central automation devices and decentralized field devices, through a serial connection. Technical developments are the PROFIBUS DP / V1 and the PROFIBUS-DP / V2.

PROFIBUS PA (Process-Automation)

… which is primarily used in the field of process engineering, is responsible for communication between measuring and process equipment or between actuators and process control systems.

PROFIBUS FMS (Fieldbus Message Specification)

… was intended in automation technology for complex machinery and equipment. Recently, this variant has been adopted gradually by PROFIBUS DP. Nevertheless, we continue to offer communication and diagnostic solutions for the entire PROFIBUS protocol family.


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isPro USBx12

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Our mobile USB adapter allows quick connection to a PROFIBUS network. Tasks such as parameterization or diagnosis can be made on-site with a laptop.
The device contains a PROFIBUS master, which controls the protocols DP and DP / V1, but is just as well usable for less common protocols such as PROFIBUS FMS.


The DIN rail modules of the product range isNet Line are available for stationary access to remote parts of the plant from a control station. With that, gateways can be realized from Ethernet to PROFIBUS DP and also to PROFIBUS PA. Besides tasks such as remote diagnostics or remote commissioning, these modules can also be used as a gateway between PROFINET and PROFIBUS or between Modbus TCP and PROFIBUS. Because of the module series’ modular and extensible design, all system components can be connected with classical wiring via a single gateway to higher-level modern Ethernet Fieldbuses.

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isNet DP

PROFIBUS DP Mastermodul
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isNet DiagM PA

PROFIBUS PA Diagnostic / Master Module
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PROFIBUS Diagnostic Tools

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isNet DPMon

PROFIBUS DP Diagnostic / Monitoring Module
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isNet PAMon

PROFIBUS PA Diagnostic / Monitoring Module
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For remote monitoring of the network infrastructure, the gateways of the isNet Line can be expanded to include modules for analyzing the communication quality. These modules detect errors on the PROFIBUS and provide a list of participants of the network, an extensive error statistics and a freely configurable event log as well as the possibility to record the data traffic for further analysis. To assess the signal waveform, the modules also include an oscilloscope with extensive trigger functions such as edge trigger, error trigger or trigger on certain telegrams or subscriber addresses.