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APPENDIX
Appendix 1 I/O Control Mode
The CPU supports two types of I/O control modes; the direct mode and refresh
mode.
Appendix 1.1 Direct mode
In the direct mode, input signals are imported to a programmable controller every
time they are input and treated as input information. The operation results of a
program are output to the output data memory and the output modules. The
following diagram shows the flow of I/O data in the direct mode.
Data memory for inputs (X)
Test operation using peripheral device
Link refresh of MELSECNET/H
Writing from serial communication
modules, etc.
Data memory for outputs (Y)
Executing the OUT instruction in the
sequence program
Test operation using peripheral device
Writing from serial communication
modules, etc.
Programmable controller
CPU
(Operation processing)
Input
module
Output
module
Y70
X0
Y75
1)
2)
3)
4)
5)
• When the input contact instruction is executed:
An OR operation is executed in the input information 1) from the input module and
input information 2) in the data memory. Then the result is used as input
information 3) at sequence program execution.
• When the output contact instruction is executed:
Output information 4) is read from the data memory for output (Y), and a sequence
program is executed.
• When the output OUT instruction is executed:
The operation result 5) of the sequence program is output to the output module,
and is stored in the data memory for output (Y).
• When the QCPU executes I/O in the direct mode, a sequence program uses DX
for inputs and DY for outputs.