Page 23 - AUTOMATION EISBN

Central processing Unit (CPU)

• The CPU controls, monitors and supervises alloperations within PLC.

• It is also caries out programmed instructions stored in the memory.

• An internal communications highway also knownsas a bus system, carries

information to and from CPU, memory and I/O units under the control of the

CPU

Memory Unit

• For storage of programs

• The user’s ladder logic program, the state of I/Oin the memory of PLC

• The main program and the other programs necessary for the operation of

PLC

• The organization of the data and information inthe memory is called

memory map

• 2 types of memory ROM (Read Only Memory) and RAM (Random
Access Memory)

Display and Indicator Unit

• Console LCD Display

• Monitor Screen

Input and Output Unit

• The I/O unit is the interface unit has function to convert the input signal and

output signal so that the CPU can communicate with the external

apparatuslike switch, stepping motor, solenoid, sensor, etc.

• 2 types of I/O – Digital I/O and Analog I/O

• Example of Input: Switch, Sensor
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