Field name
Example (hex)
Write data LO (Register 4: 1049)
00
Write data HI (Register 4: 1050)
02
Write data LO (Register 4: 1050)
E2
Error check (CRC)
–
Response
The normal response returns the follower address, function code, starting address, and quantity of registers preset.
Table 81: Response
Field name
Example (hex)
Follower address
01
Function
10
Starting address HI
04
Starting address LO
19
Number of registers HI
00
Number of registers LO
02
Error check (CRC)
–
8.10.8 Read/Write Multiple Registers (17 hex)
Description
This function code performs a combination of 1 read operation and 1 write operation in a single MODBUS transaction. The write
operation is performed before read.
Query
The query message specifies the starting address and number of holding registers to be read as well as the starting address, number
of holding registers, and the data to be written. Holding registers are addressed starting at 0. Example of a request to set
parameter
1-24 Motor Current
to 738 (7.38 A) and read
parameter 3-03 Maximum Reference
which has value 50000 (50,000 Hz):
Table 82: Query
Field name
Example (hex)
Follower address
01
Function
17
Reading starting address HI
0B (Register address 3029)
Read starting address LO
D5 (Register address 3029)
Quantity to read HI
00
Quantity to read LO
02 (
Parameter 3-03 Maximum Reference
is 32 bits long, that is, 2 registers)
Write starting address HI
04 (Register address 1239)
Write starting address LO
D7 (Register address 1239)
Quantity to write HI
00
Quantity to write LO
02
AJ363928382091en-000101 / 130R0983
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RS485 Installation and Set-up
VLT® Flow Drive FC 111
Design Guide