Modbus installation for DEIF AGC-4

  • Updated on Oct 7, 2026
  • Published on Oct 7, 2026
  • 6 minute(s) read
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This article explains how to set up a RS-485 / Modbus RTU and Ethernet / Modbus TCP/IP connection to a Calculus C06 gateway.

Scope

This guide covers two communication routes between a DEIF AGC-4 and a Calculus C06: Modbus RTU over RS-485 and Modbus TCP/IP over Ethernet. It focuses on the DEIF communication options, controller settings, physical connection and commissioning checks. Calculus gateway registration and platform configuration are outside the scope of this document.

Objective

A technician must be able to identify the installed communication option, configure the AGC-4, connect it correctly to the Calculus C06 and verify communication.

Hardware options required

Modbus RTU requires DEIF option H2 in slot 2. Modbus TCP/IP requires DEIF option N with the RJ45 Ethernet interface. If the required hardware option is not installed, that communication route is not available.

Satefy first

  • Carry out communication wiring de-energised where the installation procedure requires it.

  • Keep clear of mains, generator and breaker power terminals.

  • Only change the communication parameters listed in this guide.

  • After commissioning, return the controller to the operating mode required by the generator application.

Caution!

Before wiring or changing settings, stop the genset and make sure it cannot start unexpectedly. Do not change generator protection, breaker or application settings as part of a Modbus installation.

Choose the communication method

Route

Use

RS-485 / Modbus RTU

AGC-4 option H2, terminals 29/30/31, to the C06 3-pin RS-485 connector. Calculus values: Slave ID 1, 9600 baud, RTU, 8N1.

Ethernet / Modbus TCP/IP

AGC-4 option N RJ45 Ethernet to the C06 Ethernet port. Calculus values: IP address 192.168.2.21 and Slave ID 1. DEIF Modbus TCP port: 502.

Project check

Choose the route that matches the installed DEIF hardware option and the assigned Calculus gateway profile. Do not select a protocol only because a connector is physically present.

Communication settings overview

Setting

RTU

TCP/IP

Required DEIF option

H2

N

Slave / Unit ID

1

1

Baud rate

9600

Not applicable

Mode

RTU

Modbus TCP/IP

Serial format

8N1

Not applicable

Controller IP

Not applicable

192.168.2.21

Subnet

Not applicable

255.255.255.0

TCP port

Not applicable

502

Option A: Modbus RTU

Configure Modbus RTU

Use this section when the AGC-4 is equipped with option H2. DEIF places the Modbus RS-485 hardware in slot 2. The communication parameters are in the external communication menu group 7510.

  1. Stop the genset and make the installation safe for commissioning.

  2. Press JUMP and open menu group 7510 External communication.

  3. Set parameter 7511 Ext. communication ID to 1.

  4. Set parameter 7512 Ext. communication baud rate to 9600.

  5. Set parameter 7513 Ext. communication mode to RTU.

  6. Verify the serial format is 8 data bits, no parity and 1 stop bit. DEIF specifies no flow control.

  7. Exit the menu and keep the controller in a safe condition until wiring and communication checks are complete.

Utility Software

The same parameters can be read or changed with DEIF Multi-line 2 Utility Software. Use the authorised access level and change only the external communication parameters required for Modbus.

Connect RS-485 to the Calculus C06

For a clear 3-wire Modbus RTU connection, use terminals 29, 30 and 31 on the AGC-4 option H2 card.

AGC-4 terminal

Function

Calculus C06

Wire

29

Data + (A)

A+ / Data+

Brown

30

Data GND

GND

Green

31

Data - (B)

B- / Data-

White

Alternative terminals

DEIF states that terminals 29 and 33 are internally connected, and terminals 31 and 35 are internally connected. Terminal 34 is not used for option H2. For this guide, use 29/30/31 so A, Data GND and B are together.

Do not earth terminal 30

DEIF explicitly states that Data GND terminal 30 must not be connected to earth. Connect it only as the communication reference conductor in the RS-485 cable.

Interpret the C06 connector correctly

The C06 RS-485 connector is 3-pin. Its apparent left-to-right order changes when the detachable connector is removed and viewed from the screw side.

Practical check

Use function and wire colour as the reference: brown = A+ / Data+, white = B- / Data-, green = GND. Do not rely only on left/right position.

RS-485 cabling and termination

  • Use a shielded twisted-pair RS-485 cable. A third conductor is used for Data GND when the 3-wire connection is applied.

  • Route communication wiring away from starter motor cables, contactors and other high-current or switching conductors.

  • Keep RS-485 topology as a bus/daisy chain and avoid long stubs.

  • Connect the cable shield to ground at one end only, and insulate the unused shield end.

  • Terminate the RS-485 line between Data+ and Data- with a resistor equal to the cable impedance at the end of the bus. Do not add termination at every device automatically.

Option B: Modbus TCP/IP

Configure Modbus TCP/IP

Use this section when the AGC-4 is equipped with DEIF option N. Option N replaces the standard interface board and provides an RJ45 Ethernet connector for CAT5 cable.

Network values

Setting

Value to use

AGC-4 IP address

192.168.2.21

Subnet mask

255.255.255.0

Calculus Slave / Unit ID

1

Modbus TCP port

502

C06 Ethernet address

Use a different IP address in the same intended subnet.

Important!

Never assign the same IP address to the AGC-4 and C06. Both devices must use different addresses in the same intended subnet.

Configure the AGC-4 IP address

  1. If option N image version 2.2x or later is installed and the AGC-4 software supports display configuration, use menu 7900 for the IP address, 7910 for the gateway address and 7920 for the subnet mask.

  2. Set the AGC-4 IP address to 192.168.2.21. The DEIF factory default subnet mask is 255.255.255.0; use the approved project subnet if it differs.

  3. After changing display network parameters, write them to the device using parameter 7905 in the IP address configuration menu.

  4. Alternatively, connect with DEIF Multi-line 2 Utility Software and use the option N configurator. Older option N versions require the configurator for network changes.

  5. After writing option N network settings, allow the Ethernet interface to restart before testing communication.

Connect Ethernet to the Calculus C06

Connect the AGC-4 option N RJ45 Ethernet connector to the Ethernet port of the Calculus C06 using a suitable Ethernet cable.

Verify the TCP/IP connection

  • Verify that option N is installed and the Ethernet link/activity indication is present.

  • Verify the AGC-4 IP address is 192.168.2.21.

  • Verify the C06 Ethernet address is different and in the same intended subnet.

  • Verify the Calculus Modbus TCP client uses Slave / Unit ID 1.

  • Verify TCP port 502 is used for Modbus TCP/IP.

  • Confirm that valid AGC-4 values are received during commissioning.

Older option N versions

DEIF documentation covers multiple option N hardware and image versions. If the display menus do not match this guide, check the option N image version in the controller and use DEIF Utility Software / option N configurator.

Check after installation

Check

Expected result

Selected route

The protocol matches the installed DEIF option and the assigned Calculus gateway profile.

RTU hardware

Option H2 is installed.

RTU wiring

29 → C06 A+ (brown), 30 → C06 GND (green), 31 → C06 B- (white).

RTU settings

Slave ID 1, 9600 baud, RTU, 8N1.

TCP hardware

Option N is installed and Ethernet link is active.

TCP addressing

AGC-4 IP 192.168.2.21, subnet 255.255.255.0, C06 on a different address in the same subnet.

TCP Modbus

Slave / Unit ID 1 and TCP port 502.

Communication

Valid Modbus values are received from the AGC-4.

Controller state

Controller returned to the required operating mode after commissioning.

Troubleshooting

Symptom

Check

No RTU response

Confirm option H2 is installed and use terminals 29/30/31.

No RTU response

Check 7511 = 1, 7512 = 9600 and 7513 = RTU.

No RTU response

Verify A / Data+ and B / Data- have not been swapped.

Intermittent RTU data

Check Data GND, shielding, cable routing and RS-485 termination.

Intermittent RTU data

Confirm terminal 30 is used only as Data GND and is not connected to earth.

No TCP response

Confirm option N is installed and the Ethernet link is active.

No TCP response

Confirm AGC-4 IP 192.168.2.21 and subnet 255.255.255.0.

No TCP response

Confirm the C06 has a different address in the same intended subnet.

TCP connected, no Modbus data

Check TCP port 502 and Calculus Slave / Unit ID 1.

Cannot change network settings

Check option N image/software version and use DEIF Utility Software / option N configurator if required.

Quick reference for the technician

Item

Value / connection

Controller

DEIF AGC-4

Route A

RS-485 / Modbus RTU

Required option

H2

Terminal 29

A / Data+ → C06 A+ (brown)

Terminal 30

Data GND → C06 GND (green)

Terminal 31

B / Data- → C06 B- (white)

Parameter 7511

Ext. communication ID = 1

Parameter 7512

Baud rate = 9600

Parameter 7513

Mode = RTU

Serial format

8 data bits, no parity, 1 stop bit

Route B

Ethernet / Modbus TCP/IP

Required option

N

AGC-4 IP

192.168.2.21

Subnet

255.255.255.0

Modbus TCP port

502

Calculus Slave / Unit ID

1

Final check

  • Controller stopped and installation safe

  • Correct communication route selected

  • RTU if used: option H2, 7511 = 1, 7512 = 9600, 7513 = RTU

  • RTU if used: terminals 29/30/31 and C06 connector checked

  • TCP/IP if used: option N and Ethernet link checked

  • TCP/IP if used: IP 192.168.2.21, subnet 255.255.255.0, port 502 and Slave / Unit ID 1 checked

  • Communication confirmed during commissioning

  • Controller returned to the required operating mode

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