120 Ω

2. Hardware Implementation of the LUFP7 Gateway

2.5.3.Wiring Recommendations for the Modbus Network

• Use a shielded cable with 2 pairs of twisted conductors,

• connect the reference potentials to one another,

• maximum length of line: 1,000 metres

• maximum length of drop line / tap-off: 20 metres

• do not connect more than 9 stations to a bus (slaves and one LUFP7 gateway),

•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,

•adapt the line at both ends using a line terminator (see diagram and VW3 A8 306 RC termination below).

D(B) 4

D(A) 5

1 nF

— Line termination recommended at both ends of the line —

— VW3 A8 306 RC line termination —

To make it easier to connect the units using the topologies described in chapter 2.5.1 Examples of Modbus Connection Topologies, page 15, various accessories are available in the Schneider Electric catalogue:

1) Hubs, drops, taps, and line terminations:

LU9GC03 hub	This passive box has 8 female RJ45 connectors. Each of these connectors can
(“star” topology)	be connected to a Modbus slave, to a Modbus master, to another Modbus hub,
	or to a line termination.
VW3 A8 306 TF3 drop box	This passive box includes a short lead with a male RJ45 connector

(“bus”topologywithVW3A8306TF3dropboxes) allowing it to be connected directly to a Modbus slave, without having to use a different cable. It is fitted with 2 female RJ45 connectors for the connection of two Modbus cables of the VW3 A8 306 R•• type.

2-way TSXSCA62 subscriber connector. This passive box has a printed circuit fitted with screw terminals

(“bus” topology with tap boxes)	and allows the connection of 2 subscribers to the bus (2 female
	15 point SUB-D connectors). It includes the line termination when
	the connector is located at the end. It is fitted with 2 screw terminals
	for the connection of two double twisted pair Modbus cables.
TSXCA50 tap box	This passive box allows a Modbus unit to be connected to a screw
(“bus” topology with tap boxes)	terminal. It includes the line termination when the connector is
	located at the end. It is fitted with 2 screw terminals for the
	connection of two double twisted pair Modbus cables.
VW3 A8 306 RC double termination	Each of these two red passive boxes is a male RJ45 connector
(all topologies)	3 cm long containing an RC line termination (see diagram and
	illustration above). Only the abbreviation “RC” is shown on these
	boxes.