Datakom DPR-145 Panduan Pengguna - Halaman 16

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DPR-145 User Manual

6. MODBUS COMMUNICATION

The unit offers serial data communication port allowing it to be integrated in automation

systems.

The serial port is of RS-485 MODBUS-RTU standard. It is fully isolated from power

supply and measurement terminals for failure-free operation under harsh industrial

conditions.

The MODBUS properties of the unit are:

-Data transfer mode: RTU

-Serial data: 9600 bps, 8 bit data, no parity, 1 bit stop

-The answer to an incoming message is sent with a minimum of 4.3ms delay after

message reception.

Each register consists of 2 bytes (16 bits). Larger data structure contain multiple

registers.

Detailed description about the MODBUS protocol is found in the document "Modicon

Modbus Protocol Reference Guide". This document may be downloaded at:

www.modbus.org/docs/PI_MBUS_300.pdf

Supported functions:

-Function 3 (Read multiple registers)

-Function 6 (Write single register)

-Function 16 (Write multiple registers)

Error codes

Only 3 error codes are used:

01: illegal function code

02: illegal address

10: write protection (attempt to write a read_only register)

Data types

Each register consists of 16 bits (2 bytes)

If the data type is a byte, only the low byte will contain valid data. High byte is don't care.

For data type longer than 16 bits, consecutive registers are used. The least significant

-16-

V-3.0

(14.09.2016)