Intelligent Technologies Modbus to QCPort Adapter Manual
January 2006
MN05002002E (C)
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Page 44
Example Transmit Message
Read Register 40111 (nominal frequency) from an SV drive
SV drive address is 01
Read using function code 03 (read multiple holding registers)
Notice
Modbus is address based, not register based. The address is equal to 1 minus the
register; therefore register 111 is address 110, which is why to read register 111 a
0x006E (110 decimal) was written.
12897 = 0000
12898 = 0103
12899 = 006E
12900 = 0001
After the data portion is written, then write the message length (12897 = 0006) (6 bytes of
data)
The slave will then see this message 0103 006E 0001
If the Modbus transmission invokes a response on the destination port, the received
response will be placed in the Modbus receive registers.
Table 44 Modbus Pass-Through Receive Message Format
Byte
CHA CHB Data
0
12646 13148 Sequence
Number
1
Unused
2
12647 13149 Message
Length
3
Message
Length
4
12648 13150 To
Address
5
Function
Code
6
12649 13151 Data
7
Data
n
Last
data
byte
Example Receive Message
13148 = 00XX (sequence number)
13149 = 0007 (7 bytes of data)
13150 = 0103 (address 01, function code 03)
13151 = 0002 (high byte of data 00, 2 bytes of data)
13152 = 3CB9 (high byte of data 3C [60] ,low byte CRC B9)
13153 = 5500 (high byte of CRC 55, low byte n/a)
