12-5. Communication Summary of MOD-BUS (RTU) in Inverter
In MOD-BUS communication, host computer serves as master station and the inverter serves as
slave station. The message is transmitted from master station to slave station. The slave station
performs the specified function according to this command and sends back response message.
Transmission format of the command sent from the master station is composed of slave address,
function code, data and error inspection field.
In addition, transmission format of response message consists of acknowledgement filed for
details, response data and error inspection filed.
MOD-BUS communication in inverter only supports RTU mode.
・
Original transmission right belongs to the host computer.
・
Each time a command message is transmitted, the transmission right will be transferred.
Response message (normal)
The inverter conforms to MOD-BUS (RTU) communication, however, note that there are some
differences as below.
1) The inverter has only one data block.
12-6. Precautions on MOD-BUS (RTU) Communication in Inverter
2) Each data can be accessed with 1 bit or 16 bits.
[Address calculation example]
9
th
bit of address No. 123
3) Function code is supported for the following eight codes.
"Read Coils",
"Read Discrete Inputs",
"Read Holding Registers",
"Read Input Registers)",
"Write Single Coil",
"Write Single Register",
"Write Multiple Coils",
"Write Multiple Registers"
Contact address
＝
123
×
16 + 9 = 1977(dec) = H07B9
Command message
Host
computer
Inverter
A
dd
re
ss
Data
Function
code
In
sp
ec
tio
n
er
ro
r
A
dd
re
ss
Data
Function
code
In
sp
ec
tio
n
er
ro
r
170
