Read Holding Registers [03H] - Hitachi WJ Series User Manual

Chapter 11
11.2.2

Read Holding Registers [03h]

 How to read multiple holding register data on Modbus communication?
Q
 Reads the specified number of consecutive holding registers from the specified holding register
A
number.
 Examples of readings of the latest trip information (holding register number =0012h to 0017h)
from the inverter at slave address 1 are shown below.
No.
1 Slave address
2 Function code
3 Register start No. (High)
4 Register start No. (Low)
5 Number of holding registers (High)
6 Number of holding registers (Low)
7 CRC-16 (High)
8 CRC-16 (Low)
No.
1 Slave address
2 Function code
3 Number of data bytes
4 Register data 1 (High)
5 Register data 1 (Low)
6 Register data 2 (High)
7 Register data 2 (Low)
8 Register data 3 (High)
9 Register data 3 (Low)
10 Register data 4 (High)
11 Register data 4 (Low)
12 Register data 5 (High)
13 Register data 5 (Low)
14 Register data 6 (High)
15 Register data 6 (Low)
16 CRC-16 (High)
17 CRC-16 (Low)
*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. The maximum number of data that can be read is 16 registers (32 bytes). If it is exceeded,
an exceptional response of exception code "03h" is returned.
*4. Data of the number of data bytes is transferred. In this example, it is 12 bytes because of
the six holding registers.
 If the command cannot be executed successfully, an exceptional response is returned. For
!
details, refer to "11.2.9 Exceptional Responses".
Query
Field name
*1
*2
*2
*3
*3
Response
Field name
*4
11-2-3
RS485 Communication
Example
(HEX)
01
03
00
Register start No. = (Register No.)-1
11
00
6 registers
06
95
CD
Example
(HEX)
01
03
0C
00
0003h → 03d → E03 (Trip factor =
Overcurrent)
03
00
0004h → 4 (Inverter status =
during acceleration).
04
00
00
0000 04D2h → 1234d → 12.34 (Hz)
(Frequency)
04
D2
00
001Eh → 30d → 3.0 (A) (Output current)
1E
01
011Ch → 284d → 284 (VDC) (DC bus Voltage)
1C
77
3D "h" = Hexadecimal "d" = Decimal