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Concept

Concept


Products: RP-C, RP-C-EXT-KNX
Functionalities: Hardware
Product version: 2022, 2023, 2024, 7.0
2/13/2024

KNX Modbus Gateway Screw Terminals and Connector

The KNX Modbus gateway (RP-C-EXT-KNX) is equipped with two 3-position pluggable screw terminal blocks for connection to the RP-C Modbus (RS-485) network and a 2-pole PCB connector for connection to the KNX bus.

You need to configure which RS-485 port (RJ45) on the RP-C controller to use for the Modbus network. You can configure to use either the RS-485 Com A port (default: Sensor bus) or RS-485 Com B port (default: Room bus). For more information, see RP-C Communication Ports .For more information, see Allocating Flexible Ports .

Note:

For the RP-C-12A-F-24V, RP-C-12B-F-24V, RP-C-12C-F-24V, and RP-C-16A-F-230V controller models, the rating for the RS-485 Com A port, the RJ45 pinout for the RS-485 Com B port, and the labeling of the two RS-485 ports differ between different hardware versions of the controllers. For more information, see Differences Between RP-C Hardware Versions .

 
action_zoom_plus_stroke Screw terminals and connector, KNX Modbus gateway
Figure: Screw terminals and connector, KNX Modbus gateway
Screw terminals

The upper and lower screw terminal blocks are used as follows:

  • Upper: Power input from the RP-C through the controller's RS-485 port

  • Lower: Communication with the RP-C over the controller's Modbus network

Note:

The RS-485 Power Adapter (SXWNISORS485P10001) can be used to convert an RP-C controller's RS-485 port RJ45 interface to screw terminals. The adapter has a screw terminal for 24 VDC to support power supply from the controller to a device on the RS-485 based network. For more information, see Convert a BACnet/IP Controller RS-485 Interface .

Table: Screw Terminals, KNX Modbus Gateway

Terminal number

Designation

Usage

RP-C RS-485 Port

RJ45 Pin

Power input

1

–

Ground connection for supply voltage from the RP-C.

5 a

2

–

Ground connection for supply voltage. Not connected to the RP-C.

-

3

+

Positive connection for supply voltage (24 VDC) from the RP-C.

4, 7

Modbus

4

–

Ground connection for Modbus communication with the RP-C.

8 a

5

A

Data line A (RS485+) for Modbus communication with the RP-C.

3

6

B

Data line B (RS485–) for Modbus communication with the RP-C.

6

  1. RJ45 pins 5 and 8 are internally connected.
Connector

The KNX Modbus gateway uses a 4-conductor, 2-pole KNX connector for connection to the KNX bus.

Table: Connector, KNX Modbus Gateway

Connector color

Designation

Usage

Red

+

Positive connection to KNX bus

Dark gray

–

Ground connection to KNX bus

See Also

  • KNX Modbus Gateway RP-C-EXT-KNX
  • Wiring
  • Wire Sizes and Lengths for the KNX Modbus Gateway
  • RP-C Communication Ports
  • Allocating Flexible Ports
  • Differences Between RP-C Hardware Versions
  • RS-485 Power Adapter
  • Convert a BACnet/IP Controller RS-485 Interface