Modbus Protocol Description; Master-Slave Principle; Transmission Mode (Rtu) - JUMO LOGOSCREEN nt Interface Description

Paperless recorder with tft display, compactflash card and usb interfaces

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Data format

Communication between a master (PC or notebook) and a slave (paperless

recorder) using the Modbus/J-bus takes place according to the master-slave

principle, in the form of data request/instruction - response.

Slave 1

The master controls the data exchange, the slaves only have a response

function. They are identified by their device address.

The paperless recorder can be operated either as a Modbus slave,

see Chapter 5.1 Modbus slave, Page 35, or as a Modbus master,

see Chapter 5.2 Modbus master, Page 38.

In a Modbus network, only one device can be assigned with the

master function.

The transmission mode used is the RTU mode (Remote Terminal Unit). The

data is transmitted in the binary format (hexadecimal) with 8 or 16 bits for

integer values and 32 bits for float values.

The data format describes the structure of a byte transmitted.

Data word

8 bits

The data format to be used can be set, see Chapter 3.4

Configuration of the serial interfaces, Page 12.

4 Modbus protocol description

Master

Slave 2

Parity bit

Stop bit

even

odd

Slave n

Number of bits

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