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6 .10 MODBUS CONTROL
TG-300 can perform serial transmission by using a programmable controller (PLC) and MODBUS
communication. MODBUS is composed of one master PLC and 1 to 31 (maximum) slave units
( TG-300 ). In signal transmission (serial transmission) between the master and slaves, the master
always starts transmission and the slaves respond to it.
The master performs signal transmission with one slave at one time. Therefore, address numbers are
assigned to each slave in advance and the master specifies a number to perform signal transmission.
The slave which receives the command from the master executes the function and returns the
response to the master.
(1) Communication Specifications
●Interface
：RS-485, RS-422 (Communication interface card S-T/P must be mounted.)
●Synchronization
：Asynchronous
●Transmission parameter
：●Baud rate ：Selectable from 2400, 4800, 9600 BPS (constant H107
●Data length
：Fixed to 8 bits
●Parity
：Parity / no-parity, even / odd selectable (constant H108)
●Stop bit
：Fixed to 1 bit
●Protocol
：In accordance with .MODBUS
●Maximum number of units to be connected
：31 units (when RS-485 is used)
(
2) Data to be Sent/Received by Communication
Data to be sent/received by communication are run commands, frequency reference, fault contents,
inverter status and constant setting/reading.
(a) Operation Mode Selection (H002)
Select the run command and frequency reference input method in constant H002.
To provide a run command and frequency reference by communication, set this constant to settings 4
to 8. Also, without regard to this selection, monitoring of running status, constant setting/reading,
fault reset and multi-function input command from the PLC are enabled. The multi-function input
command becomes OR with the command input from control circuit terminals S2 to S6.
(b) Modbus Frequency Reference Unit (H105)
The frequency reference units from the PLC and in the frequency reference and output frequency
monitors (by communication) are selected.
The output frequency resolution of the TG-300 is 0.1 Hz. Even if the frequency reference unit is
changed to 0.01 Hz in constant Hl05, the value in the hundredth digit of 0.01 Hz of the received
frequency reference is rounded off internally. When 30000/100% in units of 0.1% is selected, the
value is rounded off in the same way.
(
c) Modbus Slave Address (H106)
The slave address number is set. It is necessary to set the address number so that it will not overlap
with the address number of another slave connected on the same transmission line.
Note：
To change the values set in constants Hl06 to Hl08 and enable new settings, it is necessary to turn
OFF the power supply, and then turn it ON again.
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