32 • vacon
modbus
Tel.+358 (0)201 2121 • Fax +358 (0)201 212 205
6
Example 2
Read the Process Data 42103…42104 with command
4
(Read Input Registers)
.
Command Master – Slave:
ADDRESS
01 hex
Slave address 1 hex (= 1)
FUNCTION
04 hex
Function 4 hex (= 4)
DATA
Starting ddress HI
08 hex
Starting address 0836 hex (= 2102)
Starting address LO
36 hex
No. of registers HI
00 hex
Number of registers 0002 hex (= 2)
No. of registers LO
02 hex
ERROR
CHECK
CRC HI
93 hex
CRC field B321 hex (= 45857)
CRC LO
A5 hex
Message frame:
01
04
08
36
00
02
93
A5
The reply to the Read Input Registers message contains the values of the read registers.
Answer Slave – Master:
ADDRESS
01 hex
Slave address 1 hex (= 1)
FUNCTION
04 hex
Function 4 hex (= 4)
DATA
Byte count
02 hex
Byte count 4 hex (= 4)
Data HI
13 hex
Speed reference = 1388 hex (=5000 => 50.00%)
Data LO
88 hex
Data HI
09 hex
Output Frequency = 09C4 hex (=2500 =>25.00Hz)
Data LO
C4 hex
ERROR
CHECK
CRC HI
F0 hex
CRC field B321 hex (= 45857)
CRC LO
E9 hex
Reply frame:
01
04
02
13
88
09
C4
F0
E9