MB5904D-4P-DB 4-port RS-232/422/485(DB9) Modbus Gateway

MB5904D-4P-DB 4-port RS-232/422/485(DB9) Modbus Gateway


Modbus TCP to Modbus ASCII/RTU converter gateway allows Modbus TCP masters to communicate with serial Modbus slave devices via RS-232/RS-485/RS-485 interfaces.

  • Manufacturer: ATOP
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Modbus is an industry-adopted communication protocol based on RTU, ASCII, and TCP protocols for various applications. The Modbus Gateway is capable of implementing the Modbus protocol conversion between different hardware interfaces, thereby streamlining the process of management and application. The MB5904D features

  • Diverse Hardware Infrastructure
  • Switching between Modbus Protocols
  • Modbus ID Routing
  • Simple Integration for Complex Configurations

The MB5904D series supports the three most commonly used serial communication interfaces, RS-232, RS-422 and RS-485. It also provides a web-based configuration UI, so the users can select the serial interface easily.


  • 2 x 10/100 Mbps fast Ethernet ports
  • 4 x Software-selectable RS-232/RS-485/RS-422 serial ports, up to 921kbps
  • Bi-Directional Modbus TCP/RTU/ASCII conversion from Serial to Ethernet and vice versa, VirtualCOM support, advanced Modbus Options available
  • Configuration via Web Browser/ Serial Console/ Telnet Console/ Utility
  • Monitor, manage and control industrial field devices remotely
  • Rugged metal housing with DIN rail mounting
    • SKU
    • Weight
      1 kg
    • Dimensions (L x W x H)
      12 x 6 x 15 cm


  • Input: 12 to 48 VDC (screw terminals) 
  • Consumption: 8W max


  • Interface: RS-232/422/485 software selectable 
  • Port(s): 4
  • Baud rate: 1200 bps to 921 Kbps 
  • Parity: None, Odd, Even, Mark, Space 
  • Data bits: 7,8
  • Stop bits: 1,2
  • Flow control: 
    • None
    • Software: Xon/Xoff
    • Hardware: RTS/CTS
  • Connector: 9-pin D-Sub 


  • Transmission rate: 10/100M 
  • Port(s): 2
  • Connector: RJ-45
  • Compliance: IEEE802.3 
  • Auto MDI/MDI-X: Yes

Link mode

  • Modbus TCP: Yes
  • Modbus ASC: Yes
  • Modbus RTU: Yes


  • Configuration: Web Page / Telnet / Serial console / Windows utility 
  • Atop tool: DeviceView 
  • Support protocol: Modbus TCP/ASC/RTU, SNMP, HTTP 


  • Operating temperature: -40 to 80 °C 
  • Storage: -40 to 85 ºC, 5 to 95% RH


  • EMC: FCC Class A, CE Class A


  • W x H x D: 55 x 145 x 113 mm


The converter has a DE-9 male connector for the serial port. The optional ATO-148 adapter brings these signals out to screw terminals. The pin out of the connector is shown in the installation guide.

Faulty Goods and Warranty

Where such goods have been supplied we undertake to repair or replace them as quickly as possible.Prior to returning faulty items, please contact us with a description of the fault as one of our engineers might be able to assist you by resolving the issue over the phone.
A Warranty form must be filled out and returned with any goods.

Our standard warranty period is 12 months from the date of purchase unless stated otherwise.

Other warranty periods:

Labjack Products: 5 Years
Atop Products: 3 Years
MeanWell Products: 3 Years
Terracom Products: 3 Years

Warranty is subject to us being satisfied that a defect was caused by defective workmanship or materials and was not caused by or was not substantially contributed to by other factors beyond our control including incorrect installation, alterations or modifications of the product not recommended by the manufacturer.

Returns Policy

If you are dissatisfied with our goods you may return them within 14 days of the dispatch date. Contact us for an authorisation and we will refund your purchase less shipping costs and restocking fees. All returned goods MUST be in AS NEW condition including ALL PACKAGING and DOCUMENTATION / MANUALS etc.

Please note:

  • The product returned will attract a 20% restocking fee.
  • The customer must pay the delivery costs.
  • Non standard, custom made or a specially manufactured or imported products are not returnable.
  • Semiconductors, books and software are not refundable

Full Terms and Conditions

By placing an order with Ocean Controls, you agree to be bound by our Terms and Conditions of Trade.