Modbus TCP to Serial RTU/ASCII Gateway

The STM-501C, MODBUS gateway allows the legacy MODBUS RTU/ASCII devices to operate on a MODBUS TCP network. It allows either MODBUS serial master or slave to communicate with MODBUS TCP's slave or master.

Modbus TCP masters to Modbus RTU/ASCII slaves:The STM-501C allows multiple MODBUS TCP masters to communicate with a MODBUS serial network. Since a MODBUS serial network can only handle one query at one time, queries from different masters are pipelined and processed one by one.

Modbus RTU/ASCII master to Modbus TCP slaves: When the STM-501C functions as the MODBUS RTU/ASCII master to MODBUS TCP slave gateway, the STM-501C can connect up to 8 MODBUS TCP slaves. Users can specify a UID range for each MODBUS TCP slave.

Inactive timeout: The STM-501C provides an inactive timeout that allows users to specify a time period to disconnect TCP/IP connection if there is no activity in the network. If the connection does not tear down it would occupy one connection slot and prevent any another connection again.

Configuration tools: User friendly management software provides an easy way to configure the STM-501C. It can search all serial device servers within a local area network independent of its subnet. It can also find a serial device server of a specific IP address over a wide area network. The STM-501C can also be configured by its console port or through telnet connection. The STM-501C provides a web interface for the user to configure it with a web browser.

  • DIN-Rail or Panel Mount
  • Supports 10/100 Mbps Ethernet
  • Supports RS-232, RS-422, and RS-485 Serial Interface
  • Supports LAN and WAN Communications
  • Management Access Password Protected
  • Supports up to 8 MODBUS TCP Master to MODBUS RTU/ASCII
  • Supports Inactive Timeout
  • Supports Loop Back Mode
IEEE Standards IEEE 802.3 10Base-T Ethernet
IEEE 802.3u 100Base-TX Fast Ethernet
Processing Type Store and Forward
Protocol TCP, IP, ARP, DHCP, Telnet, HTTP, UDP, ICMP
Data Bits 5, 6, 7 or 8
Stop Bits 1, 1.5 or 2
Parity none, even, odd, mark, space
Serial Buffer Output: 64K bytes
Input: 8K bytes per port
Serial Signals RS-232 - TX, RX, RTS, CTS, DTR, DSR, DCD, GND
RS-422 – TX+, TX-, RX+, RX-, RTS+, RTS-, CTS+, CTS-, GND
RS-485 - Data +, Data –, GND
Ethernet Interface
Ethernet Port Count 1 port
10/100 BASE-T(X) 1 × 10/100 BASE-T(X)
Serial Interface
Serial Port Count 1 port
Serial Interface RS-232/422/485
Other Interface
DIP Switch 2 PIN Mode Switch
LED Indicator Link,Run & Serial
Transfer Rate 110 bps to 230.4 kbps
Configuration Serial Manager,
Web UI
OS Support Windows & Linux
Utility Software Yes
Virtual COM Mode Yes
Power Requirements
Power Connection 2-pin removal terminal block
Input Voltage 7V– 30V DC
Relay Output 24V DC, 1A resistive
System Power Consumption 3 Watts
Environmental Limits
Operating Temperature 0° to 50° C (32° to 122° F)
Storage Temperature -20° to 60° C (-4° to 140° F)
Ambient Relative Humidity 5% to 95% non-condensing
Mechanical Characteristics
Housing Metal
Mounting DIN-Rail mount, Panel mount
Dimensions (W × H × D) 85 × 115 × 23 mm (3.35 × 4.5 × 0.90 inch)
Weight 0.44 lb (0.2 kg)
Regulatory Approvals
Certifications FCC,CE
Green RoHS Compliant
Warranty 5 years
  • STM-501C
  • CD Manual/Software
  • Terminal Blocks
Mini Gender Changer DB9 F/F Null Modem
Mini Gender Changer DB9 F/F Straight
Mini Gender Changer DB9 F/M Null Modem
Power Adapter for STE(W)-501/601 & LNX/IMC (US Plug). Input: AC 100-240V 50/60Hz 0.4A ; Output: DC 12V 1.25A
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