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MELSEC-Q
7 DATA COMMUNICATIONS USING BIDIRECTIONAL PROTOCOL
7.3 Processing when Simultaneous Transmission Performed During Full-Duplex
Communications
This section explains the processing when simultaneous transmissions occur in full-
duplex communication.
7.3.1 Processing when simultaneous transmissions occur
This section explains the processing performed by the Q series C24 when the external
device and the Q series C24 transmit at the same time during data communications
using the bidirectional protocol.
Since the external device and the Q series C24 do not transmit at the same time
during half-duplex communications (see User's Manual (Application) Chapter 8), this
section does not have to be read.
When an external device and the Q series C24 transmit at the same time, the Q series
C24 processing depends on the setting of "Simultaneous transmission data valid/invalid
designation" with GX Configurator-SC.
The GX Configurator-SC setting value, "Simultaneous transmission data valid/invalid
designation" is stored in the following areas of the buffer memory.
Simultaneous transmission data valid/invalid designation area (addresses: 9B
H
/13B
H
)
The Q series C24 communication data processing for each setting is described in
Section 7.3.2.
Q series C24 processing contents
Setting contents
with GX Configurator-SC
Value set to buffer memory
(Address 9B
H
/13B
H
)
Message transmit processing Message receive processing
Transmission data: Valid
Receive data: Valid
0000
H
Waits to receive the response message
(1)-2) while checking time-out after data
transmission (1)-1) is complete.
Posts normal end or abnormal end
according to whether or not the PLC
CPU received a response message
through the buffer memory.
Transmits a response message (2)-2)
after data reception (2)-1) is complete.
Posts the receive data and receive
result to the PLC CPU through the
buffer memory.
Transmission data: Invalid
Receive data: Valid
0100
H
Posts a simultaneous transmission error
to the PLC CPU through the buffer
memory after data transmission (1)-1).
Does not wait for a response massage
(1)-2) in reply to data transmission (1)-1).
Transmits a response message (2)-2)
after data reception (2)-1) is complete.
Posts the receive data and receive
result to the PLC CPU through the
buffer memory.
Transmission data: Valid
Receive data: Invalid
0001
H
Waits to receive the response message
(1)-2) while checking time-out after data
transmission (1)-1) is complete.
Posts normal end or abnormal end
according to whether or not the PLC
CPU received a response message
through the buffer memory.
Ignores data reception (2)-1) and
discards the received data.
Does not transmit a response
message (2)-2).
Does not inform the PLC CPU that
data was received.
Transmission data: Invalid
Receive data: Invalid
0101
H
Posts a simultaneous transmission error
to the PLC CPU through the buffer
memory after data transmission (1)-1).
Does not wait to a response massage
(1)-2) in reply to data transmission (1)-1).
Ignored data reception (2)-1) and
discards the receive data.
Does not transmit a response
message (2)-2).
Does not inform the PLC CPU that
data was received.
( )-m) is the number showing the correspondence with the messages in the illustration shown in Section 7.3.2.