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5.2 MEWTOCOL-COM Master Communication (RECV)
5.2.1 Reading Data from External Device
■
Procedure
PLC has the transmission right in master communication, and master communication is
performed by sending commands to, and receiving responses from, devices that support
MEWTOCOL. Data can be read by specifying unit numbers and memory addresses and
executing F146 (RECV) instruction in a user program, because PLC automatically creates
messages according to the protocol.
PLC
DT100
100
DT101
0
・・・・・・
・・・・・・・・
・・・・・・
・・・・・・・・
■
Sample program
● Send a command from the COM1 port of the unit, read data from the data areas DT400 to
DT401 of an external device (unit No. 1), and write the data into the data registers DT100 to
DT101 of PLC.
● Confirm that transmission is not in progress (SEND / RECV instruction execution flag
R913C: ON) for the same port, and start up SEND instruction.
● F146 (RECV) instruction is executed by specifying the transfer method (word transfer / bit
transfer), the number of words, unit number of a destination unit, starting address, and the
starting address of PLC memory area that stores data. Also specify the bit Nos. of both sides
in the case of bit transfer.
R0
R10
R913C
⑤
(Note 1)
The slave side may not be able to respond, when the scan time of PLC as a master unit is short and
interval between transmission sessions is short. In such cases, insert a timer instruction into the
execution conditions for instructions, and make the sending interval longer.
WUME-FPXHCOMG-02
5.2 MEWTOCOL-COM Master Communication (RECV)
Command messages
%01#RDD0040000401 (BCC) C
%01$RD64000000 (BCC) C
Response messages
Perform reading by specifying Unit number and
address using the RECV instruction
F146 RECV
DT10
④
External devices that
support MEWTOCOL-COM
DT00400 100
R
DT00401 0
・・・・・・
R
・・・・・・
F0 MV
H2
DT10
①
④
F0 MV
H1001
DT11
②
④
③
DT0
K400
DT100
⑦
⑥
・・・・・・・・
・・・・・・・・
Specification of the
transfer method and the
number of transfer words
Specification of the COM
port number of a master
unit
Execution of RECV
instruction
5-3
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