Hitachi WJ Series

Chapter 11 RS485 Communication
11-2-1
11.2 Explanation of Modbus-RTU Function Codes
11.2.1 Read Coil Status [01h]
 How to read multiple coil statuses on Modbus communication?
 Reads the coil status (ON/OFF).
 An example of read the state of input terminals 1 to 7 of the inverter at slave address 1 is shown
below. The status of input terminals 1 to 7 are as follows.
Input terminal No.
1
2
3
4
5
6
7
Coil No.
0007h
0008h
0009h
000Ah
000Bh
000Ch
000Dh
Terminal state
ON
OFF
ON
OFF
OFF
OFF
ON
Query
No.
Field name
Example
(HEX)
1
Slave address
*1
01
2
Function code
01
3
Coil start No. (High)
*2
00
Coil start No. = (Coil No.) - 1
4
Coil start No. (Low)
*2
06
5
Number of coils (High)
*3
00
6
Number of coils (Low)
*3
07
7
CRC-16 (High)
9D
8
CRC-16 (Low)
C9
Response
No.
Field name
Example
(HEX)
Input terminal 7
1
Slave address
01
Input terminal 3
2
Function code
01
Input terminal 1
3
Number of data bytes
01
4
Coil data
*4
45
45h = 0100 0101
5
CRC-16 (High)
90
6
CRC-16 (Low)
7B
*1. Broadcasting is disabled.
*2. Note that the starting number is 1 less than the actual register number. Specify a number of
"(Register No.) - 1".
*3. If the number of read coils exceeds 0 or 32, an exceptional response of exception code "03 h"
is returned.
*4. Data of the number of data bytes is transferred.
 The coil data for the response is from coil number 0007h to 000Dh with coil 0007h as LSBs
(0bit). If the coil data is not in 1byte (8-bit) units, the higher order bit is extended with zeros to
1byte (8-bit) units.
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
Coil No.
000Eh
000Dh
000Ch
000Bh
000Ah
0009h
0008h
0007h
Coil state
OFF
ON
OFF
OFF
OFF
ON
OFF
ON
45h
0
1
0
0
0
1
0
1
A
!
Q