Mitsubishi Electric MELSEC iQ-R Series User Manual page 281

Handling of received data by C24
• When a user frame (start frame, final frame) registered to C24 is received, the reception processing by user
frame is performed.
• Of the start frame No. and final frame No. (maximum 4 sets) set in default by the user for the user frame
specification for receiving area in buffer memory, the set number (nth) of the user frame received from the
target device is stored to the receive user frame storage area.
• When a transparent code for receiving is specified, the additional code data included in the arbitrary data
portion is deleted immediately after reception (or, before conversion when ASCII-BIN conversion is
performed).
Reception with the start frame (combination 1-A to C) (reception using Method 0)
■Reception of combination (1-A)
This is a method that any data portion of a reception message which can be handled by the CPU module side is enclosed by
a start frame and a final frame and transmitted from a target device.
C24 starts the reception processing when data of the same arrangement as the start frame is received.
When data of the same arrangement as the final frame is received, the arbitrary data is stored in the receive area on the buffer
memory and a read request is issued to the CPU module.
Precautions
• Any received data prior to the start frame will be ignored.
• Set a data quantity that exceeds the size of the arbitrary data portion to be received for the receive end data quantity initially
set to C24.
• Reception processing by the receive end code initially set to C24 will not be performed. Received data of a receive end
code are treated as an arbitrary data portion.
Ex.
When data transmitted from a bar code reader is received
Register STX as the start frame and register ETX as the final frame according to the message format of the bar code reader.
(Data format transmitted from the bar code reader)
S
T
X
Receive data
02
H
Ignored Stored in the reception area
E
T
Data
X
(arbitrary data)
03
H
First frame : STX
Last frame : ETX
: Reception start timing
: Receive complete timing (read timing)
15 DATA COMMUNICATIONS USING USER FRAMES
279
15.2 Data Reception
15