What This Gateway Does

The G0307 connects Modbus RTU devices to a PROFIBUS PA network. It acts as a translator between the two protocols. On one side, it speaks Modbus RTU over RS485 or RS232. On the other side, it speaks PROFIBUS PA over a fieldbus segment.

If you have Modbus devices that need to be integrated into a PROFIBUS PA control system, this gateway does the job without replacing the Modbus instruments.

Who Uses It

System integrators who need to bring Modbus devices into PROFIBUS PA networks. Plant engineers modernizing older systems where Modbus instruments are still in good condition but the control system is moving to PROFIBUS. Anyone running a mixed protocol environment who wants to keep both sides working.

Two Interface Options

The gateway comes in two variants. Pick based on what your Modbus devices require:

Note: The V1.0 release currently supports only the RS485 model. The RS232 version is planned for later.

What’s Inside

The gateway has a physical block, a Modbus transducer block, and 16 function blocks: 4 analog inputs, 4 analog outputs, 4 discrete inputs, and 4 discrete outputs. These correspond to the data that moves between Modbus and PROFIBUS.

The gateway acts as the Modbus master. It polls up to 4 Modbus slave devices, reads their data, and makes that data available to the PROFIBUS PA network.

Physical Installation

The gateway is designed for DIN rail mounting. Dimensions are 112 x 70 x 50 mm. The housing is ABS plastic, and it clips onto standard 35mm DIN rails.

Terminals are arranged as follows:

• Modbus power: 24V+, GND, PE (shield)

• Modbus RS485: A+, B-, TA (termination for A+), TB (termination for B-), PE

• Modbus RS232: TxD, RxD, GND (other pins are vacant)

• PROFIBUS PA: PA+, PA-, shield

Address Setting

You can set the PROFIBUS address in two ways:

1. Hardware: Two DIP switches on the front panel (x10 and x1). Set ADDR_EN to ON, set the switches, restart the gateway.

2. Software: Set ADDR_EN to OFF, use a PROFIBUS master to send a Set_Address command.

The hardware method is more common for commissioning. The x10 switch sets the tens digit (0-16), and the x1 switch sets the ones digit (0-9). For example, x10=3 and x1=7 gives address 37. Addresses above 125 default to 125.

LED Indicators

Software Configuration

The gateway is configured using Siemens PDM with the Microcyber EDD file. Install the EDD file, and the gateway appears as a PA device in PDM.

Two configuration areas matter:

1. Communication parameters (Device → Modbus Configuration → Modbus Communication Setting):

   • Baud rate: 2400, 4800, 9600 (default), 14400, 19200

   • Stop bits: 1 or 2

   • Parity: None, Even, Odd

   • Timeout: default 300ms

   • Retry count: 0-255

   • Slave addresses: up to 4 (1 through 4 by default)

2. Register mapping (Device → Modbus Configuration → Modbus Analog Input / Analog Output / Discrete Input / Discrete Output):

   • Set data type (float, unsigned 8/16/32, signed 8/16/32, with byte order options)

   • Set function code (1, 2, 3, 4, 5, 6, or 16)

   • Set register address

   • Set scaling range (FROM_EU0, FROM_EU100, TO_EU0, TO_EU100)

   • Optionally set a status register address

GSD File Integration

The gateway includes manufacturer GSD and supports the standard PA GSD (pa139760.gsd). With the manufacturer GSD, you can configure each function block individually. The standard GSD works with predefined slot assignments.

To install the GSD file in Siemens STEP 7:

1. Open Hardware Configuration

2. Select Options → Install GSD File

3. Browse to the GSD file location

4. Click Install

After installation, the gateway appears in the device catalog. Drag it to the PROFIBUS DP bus, set the address, and add the desired modules.

The module list is extensive. Available modules include:

Special Function Switches

On the board, there are four additional switches:

• RST: Reset to factory defaults. Set to ON, power cycle, then set back to OFF.

• WP: Hardware write protection. ON enables, OFF disables.

• SIM: Not used.

• ADDR_EN: Address enable. ON for hardware address setting, OFF for software address setting.

Power Requirements

The gateway needs two separate supplies:

• Bus power: 9-32 VDC

• Modbus power: 24 VDC (±20%)

Current consumption is ≤14mA.

Default Communication Settings

If you’re not sure what to set, start here:

Supported Modbus Function Codes

Operating Conditions

Technical Details

The PROFIBUS PA side uses the standard physical layer: 31.25 kbit/s, current-mode signaling. The bus can run up to 1900 meters, and with repeaters, up to 10 kilometers.

The gateway supports 4 Modbus slave devices. Each slave can provide analog inputs, analog outputs, discrete inputs, and discrete outputs. The configuration connects specific Modbus register addresses to specific PA function block channels.

Ordering Information

Browse the full Microcyber gateway product line.

Troubleshooting Quick Guide

No communication:

• Check bus cable connections and polarity

• Verify bus power is 9-32V

• Check shield grounding (single point)

• Check network topology and terminal resistors

• Look for address conflicts (temporary addresses 0xF8)

Address not responding:

• Confirm ADDR_EN switch is in correct position

• If using hardware addressing, verify both switches are set

• Address above 125 will default to 125

Modbus data not updating:

• Check baud rate, parity, stop bits match slave devices

• Verify register addresses are correct

• Check timeout setting (may need to increase for slower slaves)

• Use BAD_STATUS to identify which channel has communication issues

For additional troubleshooting support, contact Microcyber technical support.

About Microcyber

Microcyber was founded by the Shenyang Institute of Automation, Chinese Academy of Sciences. The company developed the first internationally approved FF H1 protocol stack in China and participated in drafting the EPA standard (now an IEC international standard). Microcyber is a member of FCG and PNO, and holds ISO 9001 certification.

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Download the full G0307 user manual (V2.1) – PDF download