Mitsubishi MELSEC LJ71C24, User Manual

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10 DATA COMMUNICATION USING THE NONPROCEDURAL PROTOCOL
(3) Receive data clear procedure using FROM/TO instruction
Write and read Receive data clear request (address: A8
H
/148
H
) using the
procedure described below.
When resuming data communication with an external device, resume it after
completing the receive data clear processing with the C24.
Depending on the data communication system, it may be necessary to restart
data communications with the external device after notifying the external device
from the CPU module that resumption of communications is possible.
(Clear Procedure)· ··When the CH1 side interface is used.
(1) While none of receiving, sending, and receive data clearing is being
performed, with the TO instruction, "1" is written to Receive data clear
request (address: A8
H
).
(2) Receive data clear processing is performed for the C24’s OS area (Refer to
Section 10.1.2).
(3) When receive data clear processing is completed, Receive data clear
request (address: A8
H
) becomes "0".
The following pages show an example of a program to clear receive data with the
FROM/TO instruction.
Create a program that contains the contacts (such as user flags) indicating the
following statuses in the TO instruction.
• Contacts indicating that the reception data read request (X3/XA) and reception
abnormal detection (X4/XB) are OFF
• Contact indicating that no dedicated instruction (OUTPUT/PRR/INPUT) is
currently being executed
• Contact indicating that receive data clear processing is not currently being
performed
C24 side
Receive data
clear request
(address: A8
H
)
CPU module
(Program)
TO instruction
(Write "1" to address A8H)
"0" "1" "0"
Send request
execution disabled
Receive
data clear
processing
(2)
Dedicated instruction
for sending execution
disabled, too
(3)
(1)