Frame Mode; List Of Supported Modbus Standard Functions - Mitsubishi Electric MELSEC iQ-F FX5 User Manual

Frame mode

For the FX5, the following frame modes are available. If the frame mode of the FX5 differs from the one of the target device, it
cannot be used.
Available frame modes
■RTU mode
In this mode, frames are received or sent in binary codes.
The frame specifications are compliant with the MODBUS protocol specifications.
Start Address field
3.5 character
1 byte
time or more
Error check calculation range
The error check in the RTU mode is conducted by CRC (Cyclic Redundancy Check).
The CRC field is two bytes, containing a 16 bit binary value. The CRC value is calculated by the transmitting
device, which appends the CRC to the message. The device that receives recalculates a CRC during receipt
of the message, and compares the calculated value to the actual value it received in the CRC field. If the two
values are not equal, an error occurs. (For procedure for generating of CRC, refer to Page 63 The frame
specifications)

List of supported MODBUS standard functions

The following table lists the MODBUS standard functions supported by the FX5.
Function code Function Name
01H Read coils
02H Read inputs
03H Read holding registers
04H Read input registers
05H Write single coil
06H Write single register
0FH Write multiple coils
10H Write multiple registers
:Applicable, :Not applicable
Function code Data
1 byte 0 to 252 bytes
Details
Read binary (R/W) devices
Read binary (RO) devices
Read 16 bit (R/W) registers
Read 16 bit (RO) registers
Write single binary device
Write single 16 bit register device
Write multiple binary (R/W) devices
Write multiple 16 bit (R/W) registers
END
Error check
Address field
(Start)
3.5 character
2 bytes
time or more
Accessible devices per
message
1 to 2000 points
1 to 2000 points
1 to 125 points
1 to 125 points
1 point
1 point
1 to 1968 points
1 to 123 points
4 MODBUS COMMUNICATION SPECIFICATIONS
1 byte
Broadcast Reference
 Page 66

Page 67

Page 68

Page 69

Page 70
 Page 70

Page 71
 Page 72
4.1 MODBUS Protocol
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