Autonics MP Series, User Manual For Communication

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1 Modbus RTU Protocol
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1.8 Exception response-error code
If occurs an error, send a response command and transmit each Exception Code after set(1) the
highest-level bit of received command (Function).
Slave address Function
+80 H
Exception
code
Error check (CRC16)
Low High
1Byte 1Byte 1Byte 1Byte 1Byte

ILLEGAL FUNCTION (Exception Code: 01 H): A command that is not supported

ILLEGAL DATA ADDRESS (Exception Code: 02 H)
: Starting address of queried data is inconsistent with transmittable address from the
device.

ILLEGAL DATA VALUE (Exception Code: 03 H)
: Numbers of queried data are inconsistent with the numbers of transmittable
(transferable) data from the device.

SLAVE DEVICE FAILURE (Exception Code: 04 H)
: Not properly completed the queried command (order).
Read the output status of non-existing coil 010001 (03E8 H) [ON: 1, OFF: 0] on Slave (Address
17) from Master.

Query (Master)
Slave address Function Starting address
No. of points 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
+80 H
Exception Code
Error check (CRC16)
Low High
11 H 81 H 02 H ## H ## H
CRC16