Profibus Basic Knowledge Learning--Message

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Profibus DP Simple introduction of communication protocols

First, the Profibus DP Communication protocol is a single, consistent communication protocol for all plant automation and process automation.

This protocol uses "master-slave" mode: one Device (master) controls one or more other devices (from);

Protocol use: "token" mode: "token" is passed through the network, the station with the token control has access to the network.

Profibus DP exists in three versions:

DP-V0:OVERALL command structure cyclic data exchange

DP-V1: Extended to non-cyclic data exchange, etc.

DP-V2: Further expansion to timely, clock synchronization and so on.

A single protocol that adapts to all applications

Profibus DP supports all DCs or controllers with a single field device;

Plant equipment and process equipment are directly connected to the Profibus DP;

Process automation equipment (PA), aggregated in the "PA cluster", connected to the Profibus DP via a connector or chain ring;

The Profibus Bus Access Protocol (second tier) is the same for three versions of Profibus (FMS/DP/PA);

This makes communication transparent and FMS/DP/PA network area easy to combine;

Because the FMS/DP uses the same physical media (RS-485/FO), they can be combined on the same cable.

Ii. Characteristics of profibus-Bus Access Protocol

Hybrid Bus Access Protocol:

Logical token ring between main stations

Master-Slave protocol between master and slave stations

Main station:

The active station has control over the bus for a limited period (Token hold time).

From Station:

Slave just responds to a request from a master, they have no control over the bus.

Iii. features of the profibus-Bus Access Protocol (FDL)

The master or slave can be connected or disconnected at any point in time, and the FDL will automatically reorganize the token ring;

Token scheduling ensures that each master has sufficient time to perform its communication tasks, so that the user must calculate the time of the entire target token ring;

The bus access Protocol has the ability to detect faulty stations, failed tokens, duplicate tokens, transmission errors, and all other possible network failures.

All information, including token information, ensures a high level of security during the transfer process to avoid transmission errors. Hamming distance hd=4.

Four, profibus-token scheduling principle

In a multi-master network, token scheduling must ensure that each master has sufficient time to complete his communication tasks;

The user organizes all target token cycle times (TTR) into the communication task account of all master stations;

Each master station calculates the time it takes to complete its communication task after receiving the token, based on the following formula (TTH):

Tth=ttr-trr

Tth= time to hold the token

Ttr= Target Token cycle time

trr= Actual token cycle time

V. Structure of the PROFIBUS message

Vi. Crawling of network messages

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Profibus Basic Knowledge Learning--Message