User Manual
Chapter 8 - Modbus RTU Protocol 127
The baud rate can be selected among the following values:
Baudrate
Timeout
byte-byte
1200
33 ms
2400
16 ms
4800
8 ms
9600
4 ms
19200
2 ms
38400
1 ms
57600
668
s
76800
501
s
115200
334
s
agy0800
8.4 Modbus functions for the drive
Here following is a detailed description of the MODBUS functions implemented for the Drive. All the values listed in the
tables are hexadecimal.
8.4.1 Read Output Registers (03)
This function allows to require the value of 16-bit (word) registers containing Drive parameters. The broadcast mode is not
allowed.
Request
Together with the Drive address and the function code (03), the message contains the register starting address
(starting Address) and the number of the registers to be read; they are both stated on two bytes. The maximum
number of registers which can be read is 125. The register numbering system starts from zero (word1 = 0) for the
MODBUS and from one (word1 = 1) for the JBUS.
Example: Modbus
Drive address 25 (19hex)
Registri from 0069 (0045
hex
) to 0071 (0003
hex
).
ADDR FUNC
DATA
DATA
DATA
DATA
CRC
CRC
start
start
word# word#
Addr HI
Addr LO HI
LO
HI
LO
11
01
00
04
00
03
46
06
Response
Together with the Drive address and the function code (03), the message includes a character containing the data
byte number and some other characters containing the data. The registers require two bytes where the first one
contains the most significative section.
Example: Response to the above mentioned request.
ADDR FUNC DATA
DATA
DATA
DATA
DATA
DATA
DATA
CRC
CRC
Byte
word
word
word
word
word
word
Count 69 HI 69 LO 70 HI 70 LO 71 HI 71 LO HI
LO
19
03
06
02
2B
00
00
00
64
AF
7A
N
OTE
!
in case the register selected range includes some reserved or missing registers, the value of these
registers is set with 0.
