modbus
vacon
• 21
24-hour s358 (0)40 8371 150 • Email: vacon@vacon.com
6
6.1.1
Supported functions
Function Code
Description
Address range
03
Read Holding Registers Applies to all addresses
04
Read Input Registers
Applies to all addresses
06
Write Single Register
Applies to all addresses
16
Write Multiple Regis-
ters
Applies to all addresses
Note: Broadcasting can be used with codes 06 and 16
Table 7. Supported messages
6.1.1.1
Read Holding Registers
The query message specifies the starting register and the quantity of registers to be read. Registers
are addressed starting with zero, i.e. registers 1 to 16 are addressed as 0 to 15.
Example of a request to read registers 42001-42003 from Slave device 1:
ADDRESS
01 hex
Slave address 1 hex (= 1)
FUNCTION
03 hex
Function 03 hex (= 3)
DATA
Starting ddress HI
07 hex
Starting address 07d0 hex (= 2000)
Starting address LO
D0 hex
No. of points HI
00 hex
Number of registers 0003 hex (= 3)
No. of points LO
03 hex
ERROR
CHECK
CRC HI
05 hex
CRC field 0546 hex (= 1350)
CRC LO
46 hex
6.1.1.2
Read Input Registers
The query message specifies the starting register and the quantity of registers to be read. Registers
are addressed starting with zero, i.e. registers 1 to 16 are addressed as 0 to 15.
Example of a request to read registers 32001 from Slave device 1:
ADDRESS
01 hex
Slave address 1 hex (= 1)
FUNCTION
04 hex
Function 04 hex (= 4)
DATA
Starting ddress HI
07 hex
Starting address 07d0 hex (= 2000)
Starting address LO
D0 hex
No. of points HI
00 hex
Number of registers 0003 hex (= 3)
No. of points LO
01 hex
ERROR
CHECK
CRC HI
31 hex
CRC field 3147 hex (= 12615)
CRC LO
47 hex
6.1.1.3
Preset Single Register
The query message specifies the register reference to be preset. Registers are addressed starting
with zero, i.e. register 1 is addressed as 0.