Hitachi WJ C1 Series

Chapter 11 RS485 Communication
11-2-10
11.2.8 Read/Write Multiple Holding Registers [17h]
 How to read and write multiple holding register data on Modbus communication?
 In succession write consecutive multiple holding register data.
 The following shows an example in which 50.00 Hz is written to "Output-frequency setting
[F001]" of inverter at slave address 1 and "Output frequency monitor [d001]" is read.
Query
No.
Field name
Example
(HEX)
1
Slave address
*1
01
2
Function code
17
3
Read register start No. (High)
*2
10
Register start No. = (Register No.) - 1
4
Read register start No. (Low)
*2
00
5
Number of read registers (High)
*3
00
6
Number of read registers (Low)
*3
02
7
Write register starting No. (High)
*2
00
Register start No. = (Register No.) - 1
8
Write register starting No. (Low)
*2
00
9
Number of write registers (High)
*3
00
10
Number of write registers (Low)
*3
02
11
Number of write data bytes
04
12
Write data 1 (High)
00
0000 1388h = 5000d → 50.00 (Hz)
13
Write data 1 (Low)
00
14
Write data 2 (High)
13
15
Write data 2 (Low)
88
16
CRC-16 (High)
F4
17
CRC-16 (Low)
86
Response
No.
Field name
Example
(HEX)
1
Slave address
01
2
Function code
17
3
Number of read data bytes
*3
04
4
Read data 1 (High)
00
0000 1388h = 5000d → 50.00 (Hz)
5
Read data 1 (Low)
00
6
Read data 2 (High)
13
7
Read data 2 (Low)
88
8
CRC-16 (High)
F4
9
CRC-16 (Low)
71
*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 number of data bytes" is not the number of holding registers, but the number of bytes
to be actually written/read. The maximum number of data that can be written/read is 16
registers (32 bytes). If it is exceeded, an exceptional response of exception code "03h" is
returned.
 If the command cannot be executed successfully, an exceptional response is returned. For
details, refer to "11.2.9 Exceptional Responses".
 Modbus communication of WJ-C1 has restrictions on writing to "2 register length parameter".
For details, refer to "Exception code 27h" in "11.2.9 Exceptional Responses".
A
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