2.1 Master-Slave principle
Communication between a master (e.g. PC) and a slave (e.g. measuring and
control system) using Modbus takes place according to the master-slave
principle, in the form of data request/instruction - response.
The master controls the data exchange, the slaves only have a response
function. They are identified by their device address.
2.2 Transmission mode (RTU)
The transmission mode used is the RTU mode (Remote Terminal Unit). Data is
transmitted in binary format (hexadecimal) with 8 bits. The LSB (least
significant bit) is transmitted first. The ASCII operating mode is not supported.
Data format
The data format describes the structure of a character transmitted. The
following data format options are available:
All manuals and user guides at all-guides.com
Slave 1
Data word
Parity bit
8 bits
—
8 bits
even
8 bits
odd
8 bits
—
2 Protocol description
Master
Slave 2
Stop bit
Number of
1/2 bit
bits
1
1
10
1
10
2
10
Slave n
9
7