3 DATA COMMUNICATION USING NONPROCEDURAL PROTOCOL
3.1 Receiving Data from Target Device
53
3
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
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.
Method Application
Reception by the receive end code Receives variable length messages.
Reception by the receive end data quantity Receives fixed length messages.
Reception by a timeout of the no-reception monitoring time
(timer 0)
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
ABCDE FGH
10
STX
D
F
H
B
A
G
E
C
ETX
(00
H
)
(0A
H
)
(41
H
)
(02
H
)
(43
H
)
(42
H
)
(45
H
)
(44
H
)
(47
H
)
(46
H
)
(03
H
) (48
H
)
(02
H
) (41
H
) (42
H
) (43
H
) (44
H
) (45
H
) (46
H
) (47
H
) (48
H
) (03
H
)
S
T
X
E
T
X
INPUT
CH1/CH2
X3/XA
C24
Reception area
(buffer memory)
CPU module
Head data
Receive complete code
Receive data
count
Target device
Reception data
read request
INPUT instruction
Received data
Transmitted
data
Description Control timing
Reception data read request
INPUT instruction
INPUT instruction completion device
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