Hitachi X200 Series Explanation of function codes, Read Coil Status 01h, Data, Field Name

B−10

Explanation of function codes

Read Coil Status [01h]:

This function reads the status (ON/OFF) of selected coils. An example follows below.

•Read intelligent input terminals [1] to [5] of an inverter having a slave address “8.”

Appendix B

•This example assumes the intelligent input terminals have terminal states listed below.

Item			Data
Intelligent input	[1]	[2]	[3]	[4]	[5]
terminal
Coil number	7	8	9	10	11
Coil Status	ON	OFF	ON	OFF	OFF

Query:

No.	Field Name	Example
		(Hex)
1	Slave address *1	08
2	Function code	01
3	Coil start address *4	00
	(high order)
4	Coil start address *4	06
	(low order)
5	Number of coils	00
	(high order *2)
6	Number of coils	05
	(low order *2)
7	CRC-16 (high order)	1C
8	CRC-16 (low order)	91

Response:

No.	Field Name		Example
			(Hex)
1	Slave address		08
2	Function code		01
3	Data size (in bytes)		01
4	Coil data *3		05
5	CRC-16	(high order)	92
6	CRC-16	(low order)	17

Note 1: Broadcasting is disabled.

Note 2: When 0 or more than 31 is specified as a number of coils, error code “03h” is returned.

Note 3: Data is transferred by the specified number of data bytes (data size).

Note 4: The PDU Coils are addressed starting at zero. Therefore coils numbered 1-31 are addressed as 0-30. Coil address value (transmitted on Modbus line) is 1 less than the Coil Number.

• The data set in the response shows terminal state of coils 7 to 14.

• Data “05h = 00000101b” indicates the following assuming coil 7 is the LSB.

Item				Data
Coil Number	14	13	12	11	10	9	8	7
Coil Status	OFF	OFF	OFF	OFF	OFF	ON	OFF	ON

• When a read coil is outside the defined coils, the final coil data to be transmitted contains “0“as the status of the coil outside the range.

• When the Read Coil Status command cannot be executed normally, see the exception response.