They have register numbers from (40001 to 49999).ĬRC stands for Cyclic Redundancy check. Holding Register: It is a 16-bit register and can be read or written. They have register numbers from (30001 to 39999). Input Register: It is a 16-bit register used for input and can only be read. They have register numbers from (10001 to 19999). They have register numbers from (1 to 9999).ĭiscrete Input: It is a 1-bit register and used as inputs and can only be read. This way each slave knows after the first byte whether or not to ignore the message.ĭiscrete Output Coils: It is a 1-bit register and they are used to control discrete outputs and can be read or written. When the master requests data, the first byte it sends is the Slave address. For more information, refer software manual.Įach slave in a network is assigned a unique unit address from 1 to 127. Before using the software, following things must be known. It is a data communication test software. Modbus Slave application receives values from any Modbus Master device by using serial communication port. The software can be downloaded from the website Modbus Slave Software In this tutorial software called Modbus Slave software from Witte Software is used. To use this device there are various Modbus Software available in the internet. The Baud r ate range is 75 bps to 115200 bps, maximum up to 6 Mbps. It shows up as a Serial/COM port and is accessible from applications or hyper-terminal. This converter provides half-duplex RS-485 communication.

So, no need of external power supply for operation. The module is completely self-powered from the USB bus. There are no command structures, whatever is sent to the Virtual COM Port is automatically converted to RS485 and vice versa. This is an USB to RS485 Converter Adapter module which supports WIN7, XP, Vista, Linux, Mac OS and provides an easy to use RS485 interface by means of using COM port in the computer. Inverting Receiver Input Inverting Driver Output Non-inverting Receiver Input Non-Inverting Driver Output It is bidirectional and half duplex and has data transfer rate of 2.5 Mbps. For using RS-485 module with microcontrollers, a module called 5V MAX485 TTL to RS485 which is based on Maxim MAX485 IC is needed as it allows serial communication over long distance of 1200 meters. RS-485 Module can be connected to any microcontroller having serial port.

Ttl serial data