Mitsubishi Electric MELSEC iQ-R Series User Manual page 265

Considerations for using user frames
■Transmitting/receiving data using user frames
It is necessary to set the user frame number to be used to the buffer memory prior to data transmission/reception (receive
user frames must be set at the startup of C24).
■Data communication procedure when the number for a receive user frame is set from the CPU
module
The procedure to set a receive user frame number form the CPU module and receive data is shown below.
Receive user frame data by performing the following operations sequentially.
• Restart the CPU module when a user frame to be used for data reception was registered from the CPU module.
• Set the receive user frame number to the buffer memory at the startup of C24, and write "1" in the 'User frame use enable/
disable designation' (Un\G173/333) on the buffer memory.
• Start data reception once the value in the user frame use enable/disable designation area on the buffer memory changes to
"2".
• Check whether data is received normally from the target device.
■When additional code data is received during data reception using the nonprocedural
protocol
C24 does not assume that 1-byte data immediately after it is data for the following controls.
• Data received as the start frame, final frame for user frame (Page 250 User Frame Types and Contents During
Communication, Page 259 Transmission/Reception Processing Using User Frame Registration Data)
• Receive end code data
Therefore, do not set a user frame containing data receive additional code data as a user frame for data reception using the
nonprocedural protocol.
■Arbitrary data portion in a message received from a target device
The arbitrary data portion of a message received from a target device cannot include data with the same arrangement (same
code) as the final frame.
Ex.
User frame
Arbitrary data
(First frame)
■Data bit length of transmission specification
In the following cases, set the data bit length of the transmission specification to 8 bits.
(Set this in "Transmission Setting" of the parameter with Engineering tool for the C24 side.)
• When transmitting and receiving the sum check code of the variable data as binary data (registered code: FFH+EEH,
FFH+F0H, FFH+F4H, FFH+F6H)
• When transmitting and receiving a user frame containing data codes 80H to FFH
User frame
(Last frame)
13 CONTENTS AND REGISTRATION OF USER FRAMES FOR DATA COMMUNICATION
13.3 Considerations for Registering, Reading, and Deleting User Frames
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