Hitachi CONVENTION 14 Instruction Manual page 253

B − 10
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."
This example assumes the intelligent input terminals have terminal states listed
below.
Intelligent input
Coil number
Coil Status
Query:
No.
1
2
3
4
5
6
7
8
Note 1:
Note 2:
Note 3:
Note 4:
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.
Coil Number
Coil Status
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.
Item
[1]
terminal
7
ON
Field Name
Slave address *1
Function code
Coil start address *4
(high order)
Coil start address *4
(low order)
Number of coils
(high order *2)
Number of coils
(low order *2)
CRC-16 (high order)
CRC-16 (low order)
Broadcasting is disabled.
When 0 or more than 31 is specified as a number of coils, error code "03h" is
returned.
Data is transferred by the specified number of data bytes (data size).
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.
Item
14
OFF
Data
[2] [3] [4]
8 9 10
OFF ON OFF
Response:
Example
No.
(Hex)
08 1 Slave address
01 2 Function code
00 3 Data size (in bytes)
06 4 Coil data *3
00 5 CRC-16 (high order)
05 6 CRC-16 (low order)
1C
91
13 12 11
OFF OFF OFF
[5]
11
OFF
Example
Field Name
(Hex)
08
01
01
05
92
17
Data
10 9
OFF ON OFF
8 7
ON