Modbus-Rtu Protocol - Toshiba TOSVERT VF-nC3 Instruction Manual

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5. MODBUS-RTU protocol

The MODBUS-RTU protocol of VF-ｎC3 supports only part of the MODBUS-RTU protocol. All data
will be binary codes.
Parameter Setting
• Protocol selection (f829)
Select "MODBUS－RTU (f829 = 1) in the communication selection parameters. "TOSHIBA"
(f829=0) is set for communication protocol selection in initial shipment setting. (See "3. Com-
munication protocol.")
• Inverter number (
Inverter numbers. 0 to 247 can be specified in MODBUS-RTU. "0" is allocated to broadcast com-
munication (no return). Set between 1 and 247.
<Related Parameter: Change and set as necessary>
f800
f801
Data Exchange with Inverters
The inverters are always ready to receive messages and perform slave operation in response to
computer requests.
A transmission error will result if the transmission format does not match. The inverters will not
respond if a framing error, parity error, CRC error or an inverter number mismatch occurs. If no re-
sponse is received, the computer side recognizes that a communication error has occurred.
Transmit data again.
(1) In case spacing for more than 3.5 bytes are provided before characters, all data immediately
preceding it will be aborted. (See "3.1. About the handling of received frames.")
(2) Communication will be effective only when inverter numbers match or the communication mode
is 0 (Broadcast communication). If there is no inverter number that matches or 0 (broadcast
communication) is specified, no response is returned by any inverter.
(3) If no communication take place within the time specified using the timer function, the computer
will assume that a communication error has occurred and trip the inverter. The timer function is
disabled when the inverter is turned on or initialized. For details, see Section 6.3, "Communica-
tion time-out detection."
(4) On executing the command received, the inverter returns data to the computer. For the re-
sponse time, see Appendix 2, "Response time."
Caution:
Communication is not possible for about one second after the power is supplied to the inverter until
the initial setting is completed. If the control power is shut down due to an instantaneous voltage
drop, communication is temporarily interrupted.
)
f802
: Baud rate
: Parity
23
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