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MODBUS

26 BC7300

The MODBUS Protocol

ASCII

In ASCII mode the telegram starts with a colon ( : ) character (0x3A), and

ends with a carriage return and a line feed (CRLF) (0x0D, 0x0A). The

characters transferred are represented in the ASCII code.

Start Addres

Functio

Data LRC END

ASCII frame

charact

ers

charact

ers

charact

ers

charact

ers

charact

ers

CRLF

RTU

In RTU mode the protocol starts with a pause of 3.5 characters, and

finishes in the same way (illustrated in the diagram with T1-T2-T3-T4). The

characters permitted for transmission in all fields are hexadecimal 0... 9,

A..., F.

Start Addres

Functio

Data CRC

Check

END

RTU frame

T1-T2-

T3-T4

charact

ers

charact

ers

T1-T2-

T3-T4

1 2 ... 21 22 23 24 25 26 27 28 29 30 31 ... 47 48

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Beckhoff BC7300 Bedienungsanleitung Seite 26