Autonics ARM Series, User Manual, Page: 9 / 28

1 Modbus RTU protocol
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1 Modbus RTU protocol
1.1 Read Coil Status(Func 01–01H)
Reads output(OX reference, Coil) ON/OFF status in the Slave device.
(1) Query (Master)
Slave Address Function
Starting Address No. of Points Error Check(CRC16)
Hi(Upper) Lo(Lower) Hi(Upper) Lo(Lower) Lo(Lower) Hi(Upper)
1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte
(2) Response (Slave)
Slave Address Function Byte Count
Data
(Data) Data
(Data) Data
(Data) Error Check(CRC16)
Lo(Lower)
Hi(Upper)
1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte
If reading the output status(ON: 1, OFF: 0) of 10 within coil 000001(0000 H) to 000010(0009 H)
on Slave (Address 17) from Master.

Query (Master)
Slave Address Function
Starting Address No. of Points Error Check(CRC16)
Hi(Upper) Lo(Lower) Hi(Upper) Lo(Lower) Lo(Lower) Hi(Upper)
11 H 01 H 00 H 00 H 00 H 0A H ## H ## H
If the values range from coil 000008(0007 H) to 000001(0000 H) on the slave are “ON-ON-OFF-
OFF-ON-ON-OFF-ON”, and the values from 000010(0009 H) to 000009(0008 H)are respectively
“OFF-ON”.

Response (Slave)
Slave Address Function Byte Count
Data
(000008 to 000001)
Data
(000010 to 000009)
Error Check(CRC16)
Lo(Lower)
Hi(Upper)
11 H 01 H 02 H CD H 01 H ## H ## H
CRC16
CRC16