(Note 1) It occurs when an abnormal telegram is received. When there is a format error in the header of an
individual protocol, the communication discards the received data and a response reception timeout
occurs.
(Note 2) It occurs when the communication control I/O relays corresponding to the communication port (master
communication clear to send flag, master communication send active flag, master communication
send done result relay)are not allocated as I/O words of the CPU unit in the I/O map. It occurs only
when the number of user connections of ET-LAN is expanded and this instruction is executed
specifying the expanded connections.
■
Sample program (in the case of SCU)
● This program sends the command from the COM1 port of the CPU unit, reads the data from
the data areas DT400 to DT401 of the external device (station number 1), and writes the
data into the data registers DT100 to DT101 of the PLC.
● This program checks that the master mode is on (XC) and that sending is not in progress in
the same port (YC), and then starts up the RECV instruction.
● Using the UNITSEL instruction, specify the slot number (U0) and the COM. port number
(U1).
● In the RECV instruction, specify and execute the partner station number (U1), starting
address (DT400), data amount (U2), and PLC's starting address to store the data (DT100).
R0
Master
communication
clear to send flag
R100
UNITSEL U0 U1
RECV.US DT0U2 DT100U1 DT400
XC YC
Master
communication
sending flag
R100
RECV
execution
Settings for the communication
port
S1: Slot 0
S2：COM1
RECV execution start conditions
Clear to send flag: ON
Sending flag: OFF
RECV processing
S1: Partner unit no. (U1)
S2: Data address (DT400)
n: Data amount (U2)
D1: Data storage area (DT100)
D2: Execution result code (DT0)
■
Time chart (in the case of SCU)
Checks that the
flag is OFF
RECV execution
Master communication
sending flag
（YC,YD,YE,YF）
Master communication
sent flag
（Y0,Y1,Y2,Y3）
Data sending
Response reception
processing
clear to send flag
（XC,XD,XE,XF）
Checks that the
flag is ON
RECV Instruction executable conditions
Clear to send flag (XC,XD,XE,XF): ON
Sending flag (YC,YD,YE,YF): OFF
Sent flag (Y0,Y1,Y2,Y3):
Normal completion: OFF
Abnormal completion: ON
Sending flag (YC,YD,YE,YF):
While sending: ON, Sending done: OFF
15.5 RECV (MEWTOCOL Master / MODBUS Master)
15-32 WUME-FP7CPUPGR-12
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