Communication and addressing

Module addressing and communication parameters

The extension module and the control system communicate via the RS485 serial line using Modbus RTU protocol. For all devices to communicate you need to configure matching communication parameters for each of them. However, each module must have its own unique Modbus address within the bus.

Extension

Modules can be configured using blue-white (HW configuration) switches placed next to the power connectors, or alternatively next to the RS485 on some models. Another option is configuration via Modbus registers (SW configuration). Configuration via DIP switches offers enough options for most applications, while configuration via Modbus registers provides broader possibilities (wider range of addresses and bitrates).

HW configuration is recommended for the module's first use and the subsequent SW configuration upload.

Modules can be easily configured in Mervis, as described in this guide.

Default communication parameters (SW configuration)*:

  • Number of data bits: 8 bits (fixed)
  • Modbus address: 15
  • Bitrate: 19200 baud
  • Parity: None

*SW configuration of the module is used only when all address switches are set to 0 (OFF). Switch states are used only during the module's startup (connecting the power supply, SW reset, Master Watchdog).

Modbus registre tables for Unipi Extension:

Each Unipi Extension features a set of blue-white switches.

Extension xG18:

This module features 6 configurable switches located at the left bottom part. The switch no.6 is placed closest to the power connectors. The lone switch next to the RS485 connector serves to attach/detach terminal resistor, eg. cannot be used for configuration.

Switch:

  • n.1 → Address bit 1 (OFF - ignored, ON - value +1)
  • n.2 → Address bit 2 (OFF - ignored, ON - value +2)
  • n.3 → Address bit 3 (OFF - ignored, ON - value +4)
  • n.4 → Address bit 4 (OFF - ignored, ON - value +8)
  • n.5 → Bitrate selection (OFF - 19200, ON - 9600)
  • n.6 → Parity selection (OFF - even, ON - none)

Extension xS11, xS51:

These modules have 5 switches located next to the power connector at the module's bottom. The no.5 switch is closest to the power connector.

Switch:

  • n.1 → Adress bit 1 (OFF - ignored, ON - value +1)
  • n.2 → Adress bit 2 (OFF - ignored, ON - value +2)
  • n.3 → Adress bit 3 (OFF - ignored, ON - value +4)
  • n.4 → Bitrate selection (OFF - 19200, ON - 9600)
  • n.5 → Parity selection (OFF - even, ON - none)

Extension xS10, xS30, xS40:

These modules feature 8 switches located next to the RS485 connector at the upper part of the module. No. 1 switch is closest to the RS485 connector.

Switch:

  • n.1 → Attaches/detaches the bus terminating resistor (not related to configuration
  • n.2 → Unused
  • n.3 → Address bit 1 (OFF - ignored, ON - value +1)
  • n.4 → Address bit 2 (OFF - ignored, ON - value +2)
  • n.5 → Address bit 3 (OFF - ignored, ON - value +4)
  • n.6 → Address bit 4 (OFF - ignored, ON - value +8)
  • n.7 → Bitrate selection (OFF - 19200, ON - 9600)
  • n.8 → Parity selection (OFF - even, ON - none)

Extension xS50:

Only 3 switches are available on this module, located between the power connector and the digital input terminals at the module's bottom. Switch no. 3 is closest to the power connector.

Switch:

  • n.1 → Address bit 1 (OFF - ignored, ON - value +1)
  • n.2 → Address bit 2 (OFF - ignored, ON - value +2)
  • n.3 → AAddress bit 3 (OFF - ignored, ON - value +4)