Mitsubishi Electric FR-A700 Technical Manual page 427

(3) Message format
Query
communication
Programmable
Query Message
controller (Master)
Inverter (slave)
Data absence time
(3.5 bytes or more)
Broadcast
communication
Programmable
Query Message
controller (Master)
Inverter (slave)
Data check time
Item
Various monitors, run command
set frequency (RAM)
Parameter read/write, frequency setting
(EEPROM)
Parameter clear/all clear
Reset command
1) Query
The master sends a message to the slave (=
inverter) at the specified address.
2) Normal Response
After receiving the query from the master, the
slave executes the requested function and returns
the corresponding normal response to the master.
3) 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.
4) 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.
The slave executes the function independently of
the inverter station number setting [Pr. 117, 331]
during broadcast communication.
(4) Message frame (protocol)
Inverter response time
(Refer to the following
table for the data
check time)
Response Message
No Response
Query message from Master
Check Time
A700 F700
12ms
E700 D700
20ms
A700 F700
30ms
E700 D700
50ms
5s
No answer
Start
461
Communication method
Basically, the master sends a query message
(question) and the slave returns a response message
(response). When communication is normal, Device
Address and Function Code are copied, and when
communication is abnormal (function code or data
code is illegal), bit 7 (= 80h) of Function Code is
turned on and the error code is set to Data Bytes.
Device Address
Function Code
Eight-Bit
Data Bytes
Error Check
Response message from slave
The message frame consists of the four message
fields as shown above.
By adding the no-data time (T1: Start, End) of 3.5
characters to the beginning and end of the message
data, the slave recognizes it as one message.
Protocol details
The four message fields will be explained below.
1) 2)
ADDRESS FUNCTION
T1 8bit 8bit
PARAMETER
Device Address
Function Code
Eight-Bit
Data Bytes
Error Check
3) 4) CRC
End
DATA CHECK
L H
T1
n 8bit
8bit 8bit
2