What This Gateway Does

The G0306 connects Modbus RTU devices to a PROFIBUS DP network. It’s a protocol converter that sits between the two systems. On the Modbus side, it speaks RTU over RS485 or RS232. On the PROFIBUS side, it speaks DP.

The key difference from its sibling G0307 is the protocol. G0306 goes to PROFIBUS DP. G0307 goes to PROFIBUS PA. DP uses RS485 transmission with higher speeds. PA uses the IEC 61158-2 physical layer for process automation. Choose based on what your control system supports.

The G0306 has a feature the G0307 doesn’t: the Modbus side can be either a master or a slave. Switch via a hardware toggle. This gives you two products in one.

Two Interface Options

Pick based on what your Modbus devices require:

The V1.0 release supports only the RS485 version. RS232 is planned for later.

Two Operating Modes – Master or Slave

The gateway can operate in two modes, switched by a special function interface:

G0306-MS (Modbus Master):

• Acts as a Modbus master on the RS485/RS232 side

• Polls up to 31 Modbus slave devices (recommended no more than 10 for reliable communication)

• Converts Modbus data to PROFIBUS DP through module configuration

• 39 slots, 209 modules available

• Each module configures one Modbus message

• Maximum 37 Modbus messages per gateway

G0306-SS (Modbus Slave):

• Acts as a Modbus slave device

• Responds to an external Modbus master

• Maps PROFIBUS input/output buffers to Modbus storage areas

• 20 slots, 67 modules available

• Up to 18 mapping relationships

Switch between modes using the toggle switch. The change takes effect after a power cycle.

For detailed configuration examples of both modes, refer to the G0306 configuration guide.

Physical Installation

DIN rail mounting. Dimensions: 112 x 70 x 50 mm. Housing is ABS plastic. Clips onto standard 35mm rails.

Terminals:

Modbus power:

Modbus RS485:

Modbus RS232:

PROFIBUS DP (DB9 connector):

Nota: This gateway does not have built-in bus termination on the PROFIBUS side. If used as a bus endpoint, use a connector with integrated termination.

Full wiring details are in the G0306 installation guide.

PROFIBUS Address Setting

Two rotary switches on the front panel:

• x10 switch: sets the tens digit (0-16)

• x1 switch: sets the ones digit (0-9)

Address calculation: address = (x10 value × 10) + (x1 value × 1)

Example: x10=3, x1=7 → address = 37

Addresses above 125 default to 125. The gateway does not support address setting through the Set_Address service — hardware setting only. Set the address with the power off.

For more details on PROFIBUS DP address configuration, see the PROFIBUS DP gateway documentation.

LED Indicators

Special Function Interface

GSD File Integration

The gateway requires a GSD file for PROFIBUS DP integration. Two device IDs have been assigned:

Select the correct GSD file based on your operating mode. Install in Siemens STEP 7:

1. Open Hardware Configuration

2. Options → Install GSD File

3. Browse to the GSD file

4. Click Install

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

Each slot except the first two can be configured with a specific module. The module selection determines what Modbus data the gateway reads or writes.

For step-by-step GSD installation instructions, visit the G0306 GSD installation page.

G0306-MS Modules (Modbus Master Mode)

Overall status module (slot 1 fixed):
Displays real-time status of each Modbus message.

Control module (slot 2 fixed):
Controls Modbus scanning. Stop/start, enable/disable read/write commands, skip current message.

Modbus communication modules (slots 3-39):

Read xxx bit modules (module 4-67): Use function code 1 or 2 to read coil/discrete input data. Read 8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88, 96, 104, 112, 120, or 128 bits.

Read xxx word modules (module 68-143): Use function code 3 or 4 to read holding or input register data. Read 1 to 44 words.

Write xxx bit modules (module 144-175): Use function code 15 to write coil data. Write 8 to 128 bits.

Write xxx word modules (module 176-199): Use function code 16 to write register data. Write 1 to 32 words.

Write single coil (module 200): Function code 5. Write one coil.

Write single register (module 201): Function code 6. Write one register.

Detailed status modules (module 202-209): Monitor individual Modbus slave status (8/16/24/32 bits or bytes). Must be placed in the last valid slot.

Each communication module requires two user parameters:

• MODBUS Slave Address (0-255)

• Starting Address (the Modbus register address to read or write)

G0306-SS Modules (Modbus Slave Mode)

Overall status module (slot 1 fixed):
Displays transmission status and error detection.

Control module (slot 2 fixed):
Controls PROFIBUS output enable and clears error flags.

Mapping modules (slots 3-20):

Input xxx bit modules (module 4-19): Map Modbus storage area 0xxxx to PROFIBUS input area. Read 8 to 128 bits.

Input xxx byte modules (module 20-35): Map Modbus storage area 4xxxx to PROFIBUS input area. Read 1 to 16 words.

Output xxx bit modules (module 36-51): Map PROFIBUS output area to Modbus storage area 1xxxx. Write 8 to 128 bits.

Output xxx byte modules (module 52-67): Map PROFIBUS output area to Modbus storage area 3xxxx. Write 1 to 16 words.

Each mapping module has fixed user parameters that associate it with a specific Modbus storage area.

Modbus Storage Areas

Note: The storage identifiers (0, 1, 4, 3) identify the storage area. Subtract 1 from the displayed address to get the actual starting address. For example, discrete input start address 0000 corresponds to address 10001 in the device.

Important Usage Notes

1. After switching between MS and SS modes, power cycle the device for the change to take effect.

2. Address calculation: although one of the rotary switches is labeled 16-bit, it’s calculated in decimal. Example: 16-bit knob = 0xB, 10-bit knob = 5 → address = 11 × 10 + 5 × 1 = 115.

3. The detailed diagnostics function in G0306-MS requires both the device user parameter “MODBUS Slave Monitoring” and the corresponding gateway module. If monitoring is configured (not 0), you must add the matching status module in the last position of all configured modules.

4. If the “MODBUS Slave Monitoring” parameter doesn’t match the configured module length, some Modbus commands may be sent incorrectly.

For troubleshooting assistance, contact Microcyber technical support.

Default Communication Parameters

G0306-MS defaults:

• Data update mode: after all responses

• Write mode: always write

• Master sending interval: slave response

• Interval time: 500ms

G0306-SS defaults:

• Modbus slave address: 1

Supported Modbus Function Codes

Technical Specifications

Ordering Information

Browse the full Microcyber gateway product line.

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, HART, and PNO, and holds ISO 9001 certification.

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Download the full G0306 user manual (V2.1)