6.3 MODBUS TCP Master Communication (RECV)
R0
Clear to send
master
communication flag
R100
UNITSEL U100 U1
RECV.US DT0U2
DT100
H301 H0
X90
Y90
Sending master
communication flag
R100
Execute
RECV
Settings for communication port
S1: CPU LAN port (U100)
S1: Connection 1 (U1)
Starting conditions for RECV
execution
Clear to send flag: ON
Sending flag: OFF
Execute RECV command
S1: MODBUS command (H03)
Partner station no. (H01)
S2: Data address (H0)
n: No. of data (U2)
D1: Data saving area (DT100)
D2: Execution result code (DT0)
（
）
DF
S1
S2
S1 S2 n D1 D2
Timing chart
Confirm OFF
Execute RECV
Sending master
communication flag
(Y90 - Y9F)
Master communication
Sending done result flag
(Y70 - Y7F)
Sending data
Response reception
processing
Clear to send master
communication flag
(X90 - X9F)
Confirm ON
Conditions to enable execution of RECV
command
Clear to send flag (X90 -
X9F): ON
Sending flag (Y90 - Y9F): OFF
Sending done result flag (Y70 -
Y7F):
Normal completion: OFF
Abnormal completion: ON
Sending flag (Y90 - Y9F):
During the sending process: ON
During execution of ED command
following response reception processing:
OFF
I/O Allocation
I/O number
X90 - X9F
Clear to send master
communication flag
When connection is ON in the master communication mode, the
flag is ON.
Y90 - Y9F
Sending master
communication flag
Turns ON during sending data based on SEND/RECV command.
Turns OFF when ED command is executed following response
reception processing.
Y70 - Y7F Sending done result flag
Reports completion result of sending data in general-purpose
communication or master communication.
(Normal completion: 0, Abnormal completion: 1)
(Note 1) Each contact is used for reading the operation status. Do not write over it with a user program.
6-5
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