Total Solution for Industrial Automation
42
Appendix 2. Method of Address Allocation
4. Features
I/O X, Y respond to external devices. X is to receive the signal of input device such as
Push button switch, Limit switch and etc. Y is to convey the calculation results from
Output Device such as Solenoid Valve, Motor, Lamp and etc.
Input section X conserves the input status inside of PLC which enables to use the A,
B pin. Output section Y only uses the A-pin output.
[Figure 19] Example of I/O configuration.
[Figure 20] I/O Area Implementation Method
As in Figure 19, X, Y area have one-to-one responding area on the one pin of each
I/O Module. While PLC is scanning, it calculates with the memory (X, Y) inside of the
CPU, regardless of status of I/O Module. After the calculation, it outputs the content
of inner memory Y which responds to the output. Later, it saves the pin-status to the
inner memory X which corresponds to Input, for the next calculation.
