Field name
Example (hex)
Error check (CRC)
–
8.10.5 Read Holding Registers (03 hex)
Description
This function reads the contents of holding registers in the follower.
Query
The query telegram specifies the starting register and quantity of registers to be read. Register addresses start at 0, that is, registers
1–4 are addressed as 0–3.
Example: Read
parameter 3-03 Maximum Reference
, register 03030.
Table 76: Query
Field name
Example (hex)
Follower address
01
Function
03 (Read holding registers)
Starting address HI
0B (Register address 3029)
Starting address LO
D5 (Register address 3029)
Number of points HI
00
Number of points LO
02 – (
parameter 3-03 Maximum Reference
is 32 bits long, that is, 2 registers)
Error check (CRC)
–
Response
The register data in the response telegram is packed as 2 bytes per register, with the binary contents right justified within each byte.
For each register, the 1
st
byte contains the high-order bits, and the 2
nd
contains the low-order bits.
Example: hex 000088B8 = 35.000 = 35 Hz.
Table 77: Response
Field name
Example (hex)
Follower address
01
Function
03
Byte count
04
Data HI (register 3030)
00
Data LO (register 3030)
16
Data HI (register 3031)
E3
Data LO (register 3031)
60
Error check (CRC)
–
8.10.6 Preset Single Register (06 hex)
Description
This function presets a value into a single holding register.
Query
The query telegram specifies the register reference to be preset. Register addresses start at 0, that is, register 1 is addressed as 0.
Example: Write to
parameter 1-00 Configuration Mode
, register 1000.
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RS485 Installation and Set-up
VLT® Flow Drive FC 111
Design Guide