204
Communication operation and setting
(1) Communication specification
The communication specifications are given below.
(2) Outline
The MODBUS protocol is the communication protocol developed by Modicon for PLC.
The MODBUS protocol performs serial communication between the master and slave using the dedicated message frame.
The dedicated message frame has the functions that can perform data read and write. Using the functions, you can read
and write the parameter values from the drive unit, write the input command of the drive unit, and check the operating
status. In this product, the drive unit data are classified in the holding register area (register addresses 40001 to 49999). By
accessing the assigned holding register address, the master can communicate with the drive unit which is a slave.
NOTE
When
"1" (MODBUS RTU protocol)
is set in
Pr. 549
and "384" (38400bps) in
Pr. 118
, parameter unit (FR-PU07) is
disabled. When using the parameter unit (FR-PU07), change parameter using the operation panel.
If a communication error caused by noises occurs while "2" is set in
Pr. 502
, the inverter operation may restart after
the deceleration stop operation.
REMARKS
Set
Pr. 549 Protocol selection
to "1" to use the MODBUS RTU protocol.
When PU connector is selected as NET mode operation source (when
Pr. 551 PU mode operation command source selection
"2"),
MODBUS RTU communication operation can be performed.
Parameters referred to
Pr. 502
Stop mode selection at communication error
Pr. 779
Operation speed during communication error
Item
Description
Related
Parameter
Communication protocol
MODBUS RTU protocol
Pr. 549
Conforming standard
EIA-485(RS-485)
—
Number of connectable devices
1:N (maximum 32 units), setting is 0 to 247 stations
Pr. 117
Communication speed
Selected among 4800/9600/19200 and 38400bps
Pr. 118
Control procedure
Asynchronous
—
Communication method
Half-duplex
—
Communication
Character system
Binary (always 8 bits)
—
Start bit
1 bit
—
Stop bit length
Select from the following three types
No parity, stop bit length 2 bits
No odd parity, stop bit length 1 bit
Even parity, stop bit length 1 bit
Pr. 120
Parity check
Error check
CRC code check
—
Terminator
Not used
—
Waiting time setting
Not used
—
REMARKS
There are two different serial transmission modes: ASCII (American Standard Code for Information Interchange) mode and RTU
(Remote Terminal Unit) mode. This product supports only the RTU mode in which 1-byte (8-bit) data is transmitted as it is.
Only the communication protocol is defined by the MODBUS protocol, and the physical layer is not stipulated.
Summary of Contents for FR-D720-0.2K-G
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