Momentum Modbus Plus 170 PNT Series Guia do Utilizador descarregar pdf (Página 116)

Using the Modbus Ports

116

870USE10110 July 2004

Two-Wire Cabling Schemes for Modbus RS485 Networks Connecting

Momentum Components

Introduction Two-wire cabling schemes may be used for single master/slave or multimaster/

slave communications. Masters may be located anywhere in the network.

Length The maximum length of cable from one end of network to other is 2000 ft. (609 m).

Number of

Devices

The maximum number of devices in a network is 64 if all are Momentum devices.

Otherwise, the maximum is 32.

Termination One end of the cable run must be terminated with a terminating resistor (color code

is red).

The other end of the cable must be terminated with a terminating shunt, which

connects the transmit pair to the receiver pair (color code is blue).

Cable All devices are connected with the same pin-for-pin cable, such as the Modbus Plus

or Modbus RS485 short interconnect cable or any Cat. 5 4-twisted pair Ethernet

cable AWG#24. A master/slave system using 2-wire cabling does not require the

special master communication cable.

POTENTIAL FOR MULTIMASTER CONFLICTS

Conflicting messages to a slave module can cause problems.

Configure a multimaster network carefully to avoid masters issuing simultaneous or

conflicting commands to the same slave module.

Failure to follow this instruction can result in injury or equipment damage.

CAUTION

Description Part Number

Modbus Plus or Modbus RS485 terminating RJ45 resistor plugs (pack of 2) 170 XTS 021 00

Modbus RS485 terminating RJ45 shunt plugs 170 XTS 042 00

Description Part Number

Modbus Plus or Modbus RS485 short interconnect cable

Color code: black

170 MCI 020 10

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Momentum Modbus Plus 170 PNT Series Guia do Utilizador Página 116