Schneider Electric LUFP7 user manual Wiring Recommendations for the Profibus-DP Network, Gnd

2. Hardware Implementation of the LUFP7 Gateway

2.6.2. Wiring Recommendations for the Profibus-DP Network
•	Use a shielded cable with a twisted pair of copper conductors, preferably a type A Profibus-DP cable.
•	Connect the reference potentials to one another,
•	You may choose the transmission rate, within limits ranging from 9.6 kbit/s to 12 Mbit/s. The choice is made
	at network startup and applies to all network subscribers.
•	The maximum length of the line		(segment) is inversely proportional to the transmission rate.
		Transmission rate (bit/s)	9,6 k	19,2 k	93,75 k	187,5 k	500 k	1,5 M	3, 6 or 12 M
		Distance/segment (m)	1 200	1 200	1 200	1 000	400	200	100
		With 3 repeaters	4 800	4 800	4 800	4 000	2 000	800	400

Experience shows that these lengths may be doubled using lines with a section of 0.5 mm².

• Do not connect more than 32 master or slave stations per segment without a repeater, 127 maximum (repeaters included) with the 3 repeaters; don't use more than 3 repeaters

• Cable routing: keep the bus away from power cables (at least 30 cm), make crossings at right angles if necessary and connect the cable shielding to the earth on each unit,

• The network ends on an active line termination, at each segment end (see diagram below); many suppliers have provided their cables with switchable line terminations. The LUFP7 gateway has no internal line termination and therefore applies a 5V voltage between pins 5 and 6 of its Profibus-DP plug in order to allow for the use of an external line termination when the gateway is at the end of the line.

GND			D(A)			D(B)			+5V
	5			3			8			6	Active line
											termination
											recommended
		390 Ω			220 Ω			390 Ω			at both ends

N.B. if you use a 490 NAD 911 03 connector on each of the two stations located at segment end, you won't have to use an external line termination, since a line termination is integrated to that type of connector. However, if you must disconnect a station to which such a connector is connected, move the connector to another station on the same network so that the line termination continues to be supplied. If you do not wish to make that type of arrangement, preferably use connectors featuring a switchable line termination.

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