Mitsubishi Electric FR-D720S SC EC, Инструкция по эксплуатации

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Communication operation and settings Parameter
6 - 226
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
inverter, write the input command of the inverter, and check the operating status. In this product,
the inverter 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 in-
verter which is a slave.
The data check time related to different functions is shown in the table below:
●
Query
The master sends a message to the slave (= inverter) at the specified address.
●
Normal
Response after receiving the query from the master, the slave executes the requested
function and returns the corresponding normal response to the master.
●
Error Response
If an invalid function code, address or data is received, the slave returns it to the master.
When a response description is returned, the error code indicating that the request from the
master cannot be executed is added.
No response is returned for the hardware-detected error, frame error and CRC check error.
●
Broadcast
By specifying address 0, the master can send a message to all slaves. All slaves that received
the message from the master execute the requested function. In this communication, the
slaves do not return a response to the master.
NOTE There are two different serial transmission modes: ASCII (American Standard Code for Infor-
mation Interchange) mode and RTU (Remote Terminal Unit) mode. This product supports
only the RTU mode in which two hexadecimal coded characters are transmitted in one byte
(8 bit) data. Only the communication protocol is defined by the Modbus protocol, and the
physical layer is not stipulated.
I001227E
Fig. 6-116: Message format
Item Check Time
Various monitors, operation command, frequency setting (RAM) < 20ms
Parameter read/write, frequency setting (E²PROM) < 50ms
Parameter clear/all clear < 5s
Reset command —
Tab. 6-67: Data check time
NOTE
The inverter executes the function independently of the inverter station number setting
(Pr. 117) during broadcast communication.
Query communication
Query Message
Response Message
PLC (Master)
Inverter
(slave)
Data absence time
(3.5 bytes or more)
Inverter response time
(Refer to the following table for the data
check time)
Broadcast communication
Query Message
No Response
PLC (Master)
Inverter
(slave)