Introduction
The central processor unit (CPU) consists of a CPU control unit, an arithmetic/logic unit (ALU), and five CPU registers. The CPU control unit fetches and decodes instructions. The ALU executes the instructions.
The CPU registers contain data, addresses, and status bits that reflect the results of CPU operations.

FEATUREs
• Four Peripheral Modules
– 16-Bit Input Capture/Output Compare Timer
– Synchronous Serial I/O Port (SIOP)
– 4-Channel, 8-Bit Analog-to-Digital Converter (ADC)
– Computer Operating Properly (COP) Watchdog
• 20 Bidirectional I/O Port Pins and One Input-Only Port Pin
– High Current Source Sink on PC0 and PC1
– Mask Programmable Pullups/Interrupts on PA0–PA7, a
Keyboard Scan Feature
• On-Chip Oscillator with Connections for:
– Crystal
– Ceramic Resonator
– External Clock
– Resistor Capacitor (RC) Oscillator
• 2112 Bytes of ROM
– 48 Bytes of Page Zero ROM
– Eight Locations for User Vectors
– ROM Security
• 128 Bytes of User RAM
• Selfcheck ROM
• Memory-Mapped Input/Output (I/O) Registers
• Fully Static Operation with No Minimum Clock Speed
• Power-Saving Stop and Wait Modes