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3. Input/Output Signals
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3. Input/Output Signals
3.1 Input/Output Signal Types and Processing
The input/output signals handled in user PLC are as follows:
(1) Input/output from/to controller
(2) Input/output from/to operation board (Note 1)
(3) Input/output from/to machine
The user PLC does not directly input or output these signals from or to hardware or controller; it inputs
or outputs the signals from or to input/output image memory. For the reading and writing with the
hardware or controller, the controller will perform the input/output according to the level of the main
process or high-speed process.
Controller
Operation
board
Machine
Input/output image
memory
(device X, Y)
User PLC
Controller
(Note 1) The operation board here refers to when the remote I/O unit is installed on the communication
terminal.
Fig. 3.1-1 Concept of input/output processing
High-speed processing
input/output
Main processing
input/output
User PLC high-speed
processing
The controller outputs
the output other than the
high-speed output
designation from the
image memory to the machine.
User PLC main
processing
The controller reads the
input other than the high-speed
input designation,
and sets in the image memory.
The controller outputs
the high-speed output
designation output from
the image memory to the
machine.
The controller reads the
high-speed input
designation input, and
sets in the image memory.
P252P251
Fig. 3.1-2 Input/output processing conforming to program level