Read Holding Registers (Fn=3); Write Single Registers (Fn=6); Loopback/Maintenance (Fn=8); Preset Multiple Registers (Fn=16) - Toptech MultiLoad II Manual

Chapter 2 –MultiLoad Responses
Since Modbus addressing has been implemented in various ways over the years, to avoid confusion in
this manual, the Modbus Holding Register addresses listed are the value in the register address field in
the message. If it is necessary to know the formal Modbus Holding Register address, simply add 40001
to the register addresses listed in the manual.
1.6.1 R H R
EAD OLDING
Note: Both Modbus registers MUST be read at the same time when reading 32-bit values.
Tx:
Rx:
MBAP
1.6.2 W S R
RITE INGLE EGISTERS
Note: cannot be used for 32-bit registers.
Tx:
Rx:
1.6.3 L /M
OOPBACK AINTENANCE
Note: only loopback of command supported.
Tx:
Rx:
1.6.4 P M
RESET ULTIPLE
Note: Both Modbus registers MUST be written at the same time when writing 32-bit values.
Tx:
Start
MBAP FN=16 Register
MSB
( =3)
EGISTERS FN
Start
Register
MBAP FN=3
MSB
FN=3
Byte
Register
(+128 if
Count
error) MSB
( =6)
FN
Start
MBAP FN=6 Register
MSB
FN=6
Start
MBAP Register
(+128 if
MSB
error)
( =8)
FN
Diagnostic
MBAP FN=8
Code MSB
Diagnostic
MBAP FN=8
Code MSB
R ( =16)
EGISTERS FN
Number
Number
Start
Of
Register
Registers Registers
LSB
MSB
Number
Start
Of
Register
Registers
LSB
MSB
st
1
st
1 Next
Register Register
LSB MSB
Start
Register
Register
MSB
LSB
Start
Register
Register
MSB
LSB
Diagnostic
Data MSB
Code LSB
Diagnostic
Data MSB
Code LSB
of Byte
Count
LSB
Number
of
Registers
LSB
Next
...
Register
MSB
Register
LSB
Register
LSB
Data LSB
Data LSB
13