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PROFIBUS-DP Physical Media Connectivity

TURCK 8/1/2018

PROFIBUS-DP is an industrial network protocol that connects field I/O devices in order to eliminate hard wiring. The network connection increases device-level diagnostic capabilities, while also providing high-speed communication between devices.

PROFIBUS-DP is based on the RS-485 serial data transfer standard. In most cases, the termination and physical media rules for PROFIBUS-DP are the same as those required for RS-485 communication. A PROFIBUS-DP network supports up to 126 nodes and virtually an unlimited amount  of I/O. The bus uses a trunkline/dropline topology. Power and communication are provided via separate  cables, allowing easy segmentation of the power structure to avoid overloading.

PROFIBUS-DP is capable of running at data rates as high as 12 Mbaud. When used at high data rates, the cable drop length from the trunk to a node is severely limited. For example, when used at 12 Mbaud, nodes must be directly connected to the trunk, with no drop length allowed.

Typical System Configuration

PROFIBUS-DP Physical Media Connectivity

Basic Parts List

A typical PROFIBUS-DP system consists of the following parts:

• A - Master
• B - Power cable
• C - Communication cable
• D - Power supply

PROFIBUS-DP stations require a network master (also called a scanner) to interface the stations to the host controller. Turck PROFIBUS-DP stations are designed  to be fully compatible  with PROFIBUS-DP equipment from other manufacturers.

Cordsets

Turck offers a complete line of molded PROFIBUS-DP cordsets to facilitate network installation, resulting in a faster start-up and fewer wiring errors. The bus and drop cables are specially designed  foil-shielded, high-flex cables with very low inductance and capacitance to minimize propagation delay time. PROFIBUS-DP cables consist of a shielded and twisted data pair with a bare drain wire.

In most cases, connections of the bus cable to the stations are made using 5-pin reverse-key Eurofast (M12) connectors. A variety of stations are also available that support D9 type connections. Power for most stations is provided through  one or two 5-pin Minifast (7/8-16 UN) connectors.

Turck cordsets for the PROFIBUS-DP system are available in standard  lengths. Please contact your local sales representative to order custom lengths.

Communication Rate/Cycle Time

PROFIBUS-DP specifications define multiple transmission speeds ranging from 9.6 Kbaud to 12 Mbaud. All nodes on a network must communicate at the same rate.

The complete cycle time of a PROFIBUS-DP system is affected by several factors:

• Number of nodes being scanned
• Amount of data produced and consumed by the nodes
• Network communication rate
• Cycle time of the control program

All of these factors must be considered  when calculating the cycle time of a particular network.

Maximum Ratings

The PROFIBUS-DP bus uses a trunkline/dropline topology. The trunk is the main communication cable and requires the appropriate RS-485 termination at both ends of the trunk. Terminating resistors are available as plug-in Eurofast modules or can be built into the D9 connectors. The length of the trunk depends on the communication rate. Drops or branches off the trunk are allowed, but are greatly limited as the communication rate increases. The list below shows the maximum ratings for a trunk at different communication rates.

Communication Rate  -  Max. Segment Length
9.6 kbps  -  1200 m
19.2 kbps  -  1200 m
93.75 kbps  -  1200 m
187.5 kbps  -  1000 m
500 kbps  -  400 m
1.5 Mbps  -  200 m
12 Mbps  -  100 m