86
Modbus RTU control (RS-485 communication)
z
STEP 3: Reading from indirect reference areas
Send the following query and read the setting value or monitor set in the indirect reference areas.
Query
Field name Data Description
Slave address 01h Slave address 1
Function code 03h Reading from holding registers
Data
Register address (upper) 13h
Register address to start reading from
=Indirect reference area 0 (1340h)
Register address (lower) 40h
Number of registers (upper) 00h
Number of registers to be read from the starting register address
(6 registers=0006h)
Number of registers (lower) 06h
Error check (lower) C0h
Calculation result of CRC-16
Error check (upper) 98h
Response
Field name Data Description
Slave address 01h Same as query
Function code 03h Same as query
Data
Number of data bytes 0Ch Value of the twice the number of registers in the query=12
Value read from register address (upper) 00h
Value read from register address 1340h
=2000 (07D0h)
Value read from register address (lower) 00h
Value read from register address +1 (upper) 07h
Value read from register address +1 (lower) D0h
Value read from register address +2 (upper) 00h
Value read from register address 1342h
=100 (0064h)
Value read from register address +2 (lower) 00h
Value read from register address +3 (upper) 00h
Value read from register address +3 (lower) 64h
Value read from register address +4 (upper) 00h
Value read from register address 1344h
=30 (001Eh)
Value read from register address +4 (lower) 00h
Value read from register address +5 (upper) 00h
Value read from register address +5 (lower) 1Eh
Error check (lower) AFh
Calculation result of CRC-16
Error check (upper) 4Eh
Refer to p.109 for the operation data command.
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