Modbus Tool
Modbus is one of the industry standards for transfering data from one place to another. Commonly from one or more PLCs to a connected PC.
Modbus is "transport" agnostic, in that it works over everything from serial lines to IP-networks, however the serial port is the most common method of transportation.
Methods
Setup
This step is used to "Open" the modbus for communication, the only thing you need to specify is the protocol to use, so far you can choose between ASCII and RTU (both over a serial port).
It is also necessary to select the stream to use (usually a serial port).
Read Single Coil
Reads a single coil from the slave device and saves it in a variable, remember that addresses (both coils and registers) are 1-indexed rather than 0-indexed on the Modbus.
Write Single Coil
Write a single coil to a slave device.
Read Single Register
Read a single register in a slave device.
Write Single Register
Write a single register to a slave device.
Besides choosing the slave, register and value to write to, it is also possible to select whether the write should be done using the Write Single Register (0x06) function or the Write Multiple Registers (0x10) function - some devices prefer only to implement one of the functions.