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4. Communications

Exception

code:

Explanation:

Illegal command code:

The command code received in the command message is invalid for PLC.

Illegal device address:

The device address received in the command message is invalid for PLC.

Illegal device content:

The data received in the command message is invalid for PLC.

1. Checksum Error

- Check if the checksum is correct

2. Illegal command messages

- The command message is too short.

- Length command message is out of range.

4.3 Communication Protocol RTU mode

Communication Data Structure

9600

(Baud rate), 8 (data bits), EVEN (Parity), 1 (Start bit), 1 (Stop bit)

START

No data input ≥ 10 ms

Address Communication Address: the 8-bit binary address

Command code Command Code: the 8-bit binary address

DATA (n-1)

…….

DATA 0

Data Contents:

n × 8-bit BIN data, n≦202

CRC CHK Low

CRC CHK High

CRC Checksum:

The 16-bit CRC checksum is composed of 2 8-bit binary codes

END

No data input ≥ 10 ms

4.3.1 Address (Communication Address)

Valid communication addresses are in the range of 0~254. Communication address equals to 0 means

broadcast to all PLCs. PLC will not respond to a broadcast message. PLC will reply a normal message

to the master device when communication address is not 0.

Example, communication address should be set to 10 (Hex) when communicating with a PLC with

address 16 (Dec) (16 in Decimal = 10 in Hex)

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Delta DVP-ES2 Bedienungsanleitung Seite 609

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