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4
FUNCTIONS
4.1.2 I/O data separation prevention function
When not using the separation prevention function (Output data)
CPU module
1
3
B
D
When using the separation prevention function (Output data)
CPU module
1
3
5
7
4 - 4
The I/O data separation prevention function is a function to prevent the I/O data of the
CPU module from being unmatched with the I/O data of the master station.
The following shows an example of output data separation.
0
2
A
C
Read during
data transfer
: Area where data transmission from master station is updated
: Area where data transmission from master station is not yet updated
(1) I/O data separation prevention function
(a) The separation of I/O data occurs when the buffer memory is also read
from/written to the CPU module during the data transmission between the
buffer memory of QJ71PB93D and the master station.
(b) When the separation prevention function is used, the reading from the CPU
module is waited during the data transmission from the master station to the
buffer memory (output receive area) of QJ71PB93D, and executed after the
data transmission has been completed.
Also, the data transmission to the master station is waited until the writing
from the CPU module to the buffer memory (input send area) of QJ71PB93D
is completed, and executed after the writing has been completed.
0
2
4
6
Read after
completion of
data transfer
: Area where data transmission from master station is updated
: Area where data transmission from master station is not yet updated
QJ71PB93D
Buffer memory
1
0
3
2
B
A
D
C
Data
transmission
QJ71PB93D
Buffer memory
1
0
3
2
5
4
7
6
Data transfer
completed
MELSEC-Q
Master station
1
0
3
2
5
4
7
6
Master station
1
0
3
2
5
4
7
6
4 - 4
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