Autonics krn100 series, Руководство пользователя

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1 Modbus RTU protocol
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1.7 Exception process (Exception Response-Error Code)
If communication error occurs, it sends response command and transmits the applicable
Exception Code after setting(1) the highest-level bit of received commend (Function).
Slave Address
Function
(Command)
+80 H
Exception Code
Error Check(CRC16)
Low High
1Byte 1Byte 1Byte 1Byte 1Byte

ILLEGAL FUNCTION (Exception Code: 01 H): Command is not supported.

ILLEGAL DATA ADDRESS (Exception Code: 02 H): Starting address of the queried data is
inconsistent with transmittable data address.

ILLRGAL DATA VALUE (Exception Code: 03 H): The number of the queried data is
inconsistent with the number of transmittable data.

SLAVE DEVICE FAILURE (Exception Code: 04 H): Not properly completes the queried
command.
The below example is to read the output status (ON: 1, OFF: 0) of non-existing coil 01001(03E8
H) on the Slave(Address 17) from the Master.

Query (Master)
Slave Address
Function
(Command) Starting Address No. of Points(Number of data) Error Check(CRC16)
High Low High Low Low High
11 H 01 H 03 H E8 H 00 H 01 H ## H ## H

Response (Slave)
Slave Address
Function
(Command)
+80 H
Exception Code
Error Check(CRC16)
Low High
11 H 81 H 02 H ## H ## H
CRC16