Modbus is an open, mature, and straight forward communications protocol. It was originally published in 1979 by Modicon (Schneider Electric) and has since evolved into a standard communications protocol for industrial electronic devices.
Modbus was specifically designed to be used in supervisory control and data acquisition systems, connecting a supervisory computer with several remote terminal units (RTU). It therefore uses a master-slave-technique in which one device, the master, initiates transactions (called queries).
Other devices, slaves respond by performing the action requested in the query and/or by supplying the requested data to the master.
emModbus—Available Shipments
SEGGER offers emModbus in two distinct shipments, emModbus Master and emModbus Slave.
TCP/IP Stack
For usage of Modbus/TCP, emModbus requires a TCP/IP capable stack. emModbus can be used with any TCP/IP stack that supports BSD Standard Sockets.
Multi Tasking
Although emModbus can be used completely without a RTOS, it is recommended to use emModbus in a multi tasking system, at least when implementing a Modbus master.