Receiving Data From Target Device; Receiving Methods - Mitsubishi Electric MELSEC iQ-R Series User Manual
Serial communication module
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3.1
Receiving Data from Target Device
This section explains data reception from a target device.
Receiving methods
The following shows the methods for receiving data in any format using the nonprocedural protocol.
There are three methods for receiving data: the "reception by the receive end code" for receiving variable length messages,
and the "reception by the receive end data quantity" for receiving fixed length messages, and the "reception by a timeout of
the no-reception monitoring time (timer 0)" for the case when the receive end code and receive end data quantity have not
been determined.
The receive end code and receive end data quantity used for data reception can be changed to any setting values by the user
using Engineering tool.
C24 turns the 'CH reception data read request' (X3/XA) ON when it receives the receive end code before data equivalent to
the receive end data quantity has been received.
Therefore, when receiving data using the receive end code, set a value which is bigger than the maximum number of data
sent from the target device in the receive end data quantity designation.
For the changing methods for the receive end code and receive end data quantity, refer to the following section.
Page 74 Receive end data quantity and receive end code settings
Method
Reception by the receive end code
Reception by the receive end data quantity
Reception by a timeout of the no-reception monitoring time
(timer 0)
CPU module
Ò
Reception data
read request
Ó Ô
INPUT instruction
Description
Reception data read request
INPUT instruction
INPUT instruction completion device
When data is received from the target device using either 'reception by receive end code' or 'reception by receive end data
quantity' method, the CH reception data read request' (X3/XA) turns ON.
Application
Receives variable length messages.
Receives fixed length messages.
Receives a message of which the receive end code and receive end data quantity have not
been determined. For a specification of the non-reception monitoring time (timer 0), refer to
the following section.
Page 228 No-reception Monitoring Time (timer 0) Setting
C24
Reception area
(buffer memory)
10
Receive data
(00
)
(0A
)
H
H
count
A
STX
(41
)
(02
)
H
H
C
B
(42
)
(43
)
H
H
E
D
Received data
(45
)
(44
)
H
H
G
F
(47
)
(46
)
H
H
ETX
H
(03
)
(48
)
H
H
CH1/CH2
X3/XA
3 DATA COMMUNICATION USING NONPROCEDURAL PROTOCOL
Head data
S
A
B
C
D
E
F
T
X
(02
) (41
) (42
) (43
) (44
) (45
) (46
H
H
H
H
H
H
Transmitted
data
Control timing
INPUT
3.1 Receiving Data from Target Device
Receive complete code
Target device
E
G
H
T
X
) (47
) (48
) (03
)
H
H
H
H
3
53
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