ModbusTCP ⇔ ModbusRTU/ASCII
(LAN ⇔ RS-422/485)

Modbus TCP Gateway


Able to use in cold district up to –25°C

SI-485MB is a Modbus gateway to convert bi-directionally Modbus RTU/ASCII of serial interface to Modebus TCP of Ethernet. The firmware for gateway process supports Modbus TCP master mode and Modbu TCP slave mode and supports all the current ModbusRTU/ASCII register and command conversion. The robust metal body, broad range of temperature, wide input voltage range, and the support for installation by options such as 35mm DIN rail and wall bracket allow you to use it for factory automation without worry.


[ Connector Side ]


[ Modbus master mode ]

You can use Modbus RTU/ASCII master device as Modbus TCP master by using SI—485MB in master mode. Once the SI-485MB receives a Modbus RTU-ASCII frame (query message) from the master device of the RS-422/485, it connects to the IP address indicated in the address field of the frame or to the specified IP address and then it transmits the data in Modbus TCP frame format.

[ Modbus Slave mode ]

You can use Modbus RTU/ASCII slave devices as Modbus TCP slaves by using SI-485MB in slave mode. Once the SI-485MB receives a Modbus TCP frame (query message) from the Modbus TCP master device, it transmits the data to the RS-422/485 side in Modbus RTU/ASCII frame format. SI-485MB allows up to 10 Modbus TCP master devices, and control the shared access.


Model SI-485MB
Conversion Modbus TCP <-> Modbus RTU/ASCII 
Serial Interface RS-422/485
6 pole terminal block (Press-to-screw pitch type), Fitness wire AWG24-14/2.5mm2
Termination resistor can be set.
Synchronous Method Asynchronous
Baud Rate (bps) 300/600/1200/2400/4800/9600/19200/38400/57600/115200
Data Frame Structure Data(7 or 8) + Parity(Even, Odd or None) + Stop(1 or 2)
Protocol Modbus RTU, Modbus ASCII
Surge protection 15KV ESD
LAN Interface Ethernet IEEE802.3, RJ-45 connector, 10BASE-T/100BASE-TX
Protocol Modbus TCP
LED display 10BASE-T, 100BASE-TX, Activity, Link, Full/Half duplex
Transformer insulation 1500V
Configuration By Web Manager or by Telnet
Power Supply AC adapter or
Terminal block: DC5 to 30V from 6th pin
Consumption 1.5W
Temperature*1 Operating: -25 to 75 degree Celsius
Storage: -25 to 85 degree Celsius
Humidity 5 to 95% RH (no condensation)
Size 65 x 90 x 24 mm (W x D x H), About 200g
Accessories AC adapter, Utility CD-ROM, Instruction manual*2, Warranty
*1: Temperature specification of the attched AC adapter (GF12-US0618) is 0 to 40 degree Celsius.
*2: Only in Japanese


Description Name Model Remarks
DIN Plate DIN Plate SI-DIN70 A plate for installing 35mm DIN rail.
Magnet SI-MG70 Two magnets to attach the SI/LANIO-series on the wall. Screw two magnets on the bottom of device.
Wall bracket SI-WM1

Metal fitting to attach the device on the wall.

Screw the meal fitting board on the bottom of device.
AC adapter for SI-series GF12-US0618

Input: AC100-240V, 50/60Hz
Output: DC6V, 1.8A
Plug: Center minus, 5.5mm (external), 2.1mm (internal)

*Small, low cost AC adapter
*AC adapter attached with SI-485MB.
Wide Input AC adapter 6A-181WP09 Input: AC100-240V, 50/60Hz
Output: DC9V, 2A
Plug: Center plus, 5.5mm (external), 2.1mm (internal)