Central Processing Unit CPU

The function of the CPU is to store and run the PLC software programs. It also interfaces with the Co-Processor Modules, the I/O Modules, the peripheral device, and runs diagnostics. It is essentially the "brains" of the ethernet plc.
  The CPU, shown in Figure X, contains a microprocessor, memory, and interface adapters.
  The items shown inside the cpu module plc and their basic functions are as follows:
  The microprocessor codes, decodes, and computes data.
  The memory (ROM, PROM/EEPROM/UVPROM,and RAM) stores both the control program and the data from the field devices.
The I/O Interface adapter connects the Co-Processor Modules, the I/O Modules and the Peripheral Device to the CPU.