Hitachi SJ7002 Series Instruction Manual page 311

B–28
ModBus Mode Communications
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Query:
No. Field Name
1 Slave address *1
2 Function code
3 Register start number
(high order) *2
4 Register start number
(low order) *2
5 Change data (high
order)
6 Change data (low order)
7 CRC-16 (high order)
8 CRC-16 (low order)
Note 1: Broadcasting is disabled.
Note 2: The starting coil number is one
less than the number of the coil to
be read first.
When the Write Holding Register command cannot be executed normally, refer to the
exception response.
Loopback Test [08h]:
This function checks a master-slave transmission using any test data. An example follows:
• Send test data to an inverter having slave address "1" and receiving the test data from the
inverter (as a loopback test).
Query:
No. Field Name
1 Slave address *1
2 Function code
3 Test subcode (high
order)
4 Test subcode (low
order)
5 Data (high order)
6 Data (low order)
7 CRC-16 (high order)
8 CRC-16 (low order)
Note 1: Broadcasting is disabled.
The test subcode is for echo (00h,00h) only and not available to the other commands.
Response:
Example
No. Field Name
(hex)
05 1 Slave address
06 2 Function code
12 3 Register start number
(high order)
02 4 Register start number
(low order)
00 5 Change data (high
order)
32 6 Change data (low order)
AD 7 CRC-16 (high order)
23 8 CRC-16 (low order)
Response:
Example
No. Field Name
(hex)
01 1 Slave address
08 2 Function code
00 3 Test subcode (high
order)
00 4 Test subcode (low
order)
Any 5 Data (high order)
Any 6 Data (low order)
CRC 7 CRC-16 (high order)
CRC 8 CRC-16 (low order)
Example
(hex)
05
06
12
02
00
32
AD
23
Example
(hex)
01
08
00
00
Any
Any
AD
23