RS232 <> RS422/RS485 fully isolated converter with self configuration and automatic line turn-around


NOTE : MI400e-RD has reached the end of its life cycle (to know more about its different deadlines click here).
Your sales representative is at your disposal for any questions.


  • Self-configurable serial link parameters
  • Serial speed up to 2Mbps
  • Optional dual RS232 port in RS485 half-duplex mode
  • Automatic RS485 line turn-around
  • LED display easy RS signals monitiring & diagnostic
  • Din Rail, wall, case and rack universal mounting
  • AC or DC power supply (depending on models)
  • Connectors are compatible with the ACKSYS MI400 series, the RS422/485 screw-in terminal is compatible with the Westermo TM MA-45 & MD-45 products
  • Built-in continuous line surge protection, ESD protection, and lightening protection
  • Robust metal housing, CE standards


Thanks to the use of the latest technologies, the MI400e-RD series allows you to install easily and quickly your industrial RS422/RS485 network while making advantage of an increased reliability.

The automatic RS485 line turn-around function contributes to the simplicity of the product installation; the MI400e-RD series automatically detects the direction of the serial data and is totally independent of the communication protocol.
Its original mechanism of self configuration frees you from the tiresome operation which consists in the serial parameters setup.

Its dual port feature also makes it possible to connect two RS232 serial devices to a single RS485 bus.

The MI400e-RD series accept 2 and 4 wires RS422/485 connection, for up to 1200m and support up to 32 bus connected equipments.

Its small size, design features and its great adaptability make it a really universal product capable to fit in all the needs of the industry.

Technical characteristics





One serial RS232 port to one RS422/RS485 port with RS485 mode self line turn-around*, optional dual RS232 slave ports to the RS485 port mode.






From 50 bps to 2Mbps






Serial link parameters self configuration (auto-RTS), no switches. Line polarization, termination, echo mode and selection between RS422/RS485 modes are configurable by mini-switches.






Male SUB D 9 connector on the RS232 side, 5 pins screw-in terminal on the RS422/485 side, compatible with the Westermo™ MA-45 & MD-45 products and the MI400-x series.






LED display for TxD, RxD & RTS signals, power supply and RS422/485 line error.




Power supply


AC model works within the 85VAC to 264 VAC 47-440 Hz range and +100VDC to +370VDC (IEC-320 power cord), DC low voltage model works within the +9VDC to +36VDC range (screw-in terminal), consult us for extended power supply range.






3 Kveff/1min opto-couplers line isolation, 4 Kveff/1min transformer power line isolation, DC 2 Kveff/1min isolation.






Up to 256 RS422 / RS485 tranceivers




Input load


1/8 UL RS485




EMI-RFI protection


Built-in continuous line surge protection (50 VCA), ESD protection (15 KVeff) and lightning protection (shock wave & residual effects).




EMC & Security


NF EN 55022 emission for residential environment, NF EN 61000-6-2 immunity for industrial environment, NF EN 60950 security.






6VA for the AC model, 3,5W for the DC model






Operating temperature: from 0°C to +65°C

Relative humidity: 95% at +25°C




Dimensions, weight


80 mm (L) x 90 mm (l) x 40 mm (H), 0.5 Kg AC model, 0.4 Kg DC model






Accessories for din rail mounting and braces for wall and rack mounting delivered with all models



* Less than 15uS turn-around delay for speed < 48 Kbps, 2 bits duration turn-around delay for speed > 48 Kbps


Applications MI400e-RD 

Technical documentation


NOTE : MI400e-RD has reached the end of its life cycle (to know more about its different deadlines click here).
Your sales representative is at your disposal for any questions.

References to order





Isolated RS232 <> RS422/485 converter with self line turn-around, 85/264VAC and +100/370VDC power supply, IEC-320 power cord.






Same as MI400e-RD, +9VDC to +36VDC low voltage power supply

→ DISCONTINUED PRODUCT. Available until stock lasts.


Add the –2 suffix for the option dual RS232 port support over one RS485 port