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MELSEC-Q
7 DATA COMMUNICATIONS USING BIDIRECTIONAL PROTOCOL
7.3.2 Communication data processing when simultaneous transmissions occur
Examples of the Q series C24 communication data processing for various settings of
"Simultaneous transmission data valid/invalid designation" by GX Configurator-SC are
explained.
(1) Transmission: valid, reception: valid
Q series C24
External device
Arbitrary data
E
N
Q
Sum check
code
Arbitrary data
E
N
Q
Sum check
code
A
C
K
A
C
K
Time check
(timer 1)
1)-22)-1
1)-1 2)-2
POINT
When the entire message of 2)-1 was received while transmitting the message of
1)-1 in the illustration.
• The Q series C24 outputs the receive data read request signal of 2)-1 to the PLC
CPU after transmitting all 1)-1. (Turns on the X3/XA.)
(2) Transmission: invalid, reception: valid
External device
Arbitrary data
E
N
Q
Sum check
code
Arbitrary data
E
N
Q
Sum check
code
A
C
K
2)-1
1)-1 2)-2
Ignores the receive
data of 1)-1.
(Generates a simultaneous
transmission error.)
Q series C24
(3) Transmission: valid, reception: invalid
External device
E
N
Q
E
N
Q
A
C
K
1)-21)-1
1)-1
Q series C24
Time check
(timer 1)
Ignores the receive
data of 2)-1.
Arbitrary data
Sum check
code
Arbitrary data
Sum check
code