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Rs485 Modbus protocol

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rmrps

New Member
Hi Friends
I am new to rs485 communication i want to know how to create rs485 modbus protocol using given register value for accessing information that is read data and write data i have baud rate is 115200 data is 7, parity even stop bit is 1 and register address is
for reading data register address is D174
for write data register address is M605 and M72
slave id is 3A

Please guide me to create Rs485 Modbus protocol using the above register value
 

MaxHeadRoom78

Well-Known Member
RS285 has nothing to do with Modbus except a means of transmission.
I think you need the Modbus tutorial, there are a few out there.
Max.
 

JimB

Super Moderator
Most Helpful Member
As Max has already said, Modbus is not directly related to RS485.

Modbus is a communications protocol.
There are actually two forms of Modbus, Modbus RTU and Modbus ASCII

The message format of Modbus RTU is a series of bits, what each bits represent is up to the software guy to determine.
Modbus ASCII on the other hand, send data in the form of text messages.

If you want to implement a Modbus interface, download this document and read it thoroughly.
http://modbus.org/docs/PI_MBUS_300.pdf

RS485 is an electrical specification for the signal connection between two devices.
The form of the data passing through an RS485 interface is not defined in RS485.
It could be in Modbus format, or it could be something else.

The electrical interface for a Modbus Data link could be RS485, Rs442, or even good old RS232.
There are some systems which implement Modbus over an Ethernet connection.

JimB
 

JimB

Super Moderator
Most Helpful Member
Thread restarted by a spammer, since deleted.
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JimB
 
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