Perle Systems Technical Notes
Modbus is a legacy serial protocol used in industrial automation by equipment such as SCADA, HMI, OPC Servers, PLC’s, RTU’s and HMI’s.
ModBus comes in 2 formats ;
The Modbus protocol contains device (host) addressing and enables communication between multiple entities on same serial line ( IE: RS485 ). Modbus masters poll modbus slaves in order to send and retrieve information.
The Industrial Automation industry created the Modbus/TCP protocol which enables direct attachment of equipment over Ethernet. Equipment with support for Modbus/TCP could then be used on standard Ethernet networks providing interconnection over greater distances and with more flexibility.
Valuable legacy equipment that is limited to serial modbus connections may require attachment to ModbusTCP or Modbus/UDP compliant device (hosts) over Ethernet. Perle IOLAN Device Servers provide full support for attaching Modbus serial to Modbus/TCP equipment via the Modbus Gateway features.