8051 Family Microcontroller

Microprocessors, such as 8086 family, have only CCU and ALU in them. External RAM, ROM, and I/O are required.
Microcontrollers, such as 8051 family, encompass CCU, ALU, RAM, ROM, and I/O in a single chip.
Microcontrollers have limited computational power, but their low-cost make them prevalent in comsumer products and small-scale control systems.
We adopt 8051 family microcontroller in our class for its general structure and managable system complexity.
A large number of manufactures offer different variants of 8051 family microcontroller.

8-bit CPU optimized for control applications
128 bytes of on-chip Data RAM, 4K bytes of on-chip Program Memory (Flash Memory/ROM)
64K Program Memory address space, 64K Data Memory address space
32 bidirectional and individually addressable I/O lines
Two 16-bit timer/counters
Full duplex programmable UART
6-source/5-vector interrupt structure with two priority levels

Pin Configurations
Vcc, GND: supply voltage (5V), ground
XTAL1, XTAL2: crystal connections for system clock
RST: reset input
EA: External Access, EA=5V to enable internal ROM.
P0.0~P0.7: Port 0, bidirectional bit-addressable with open drain
P1.0~P1.7: Port 1, bidirectional bit-addressable with internal pullups
P2.0~P2.7: Port 2, bidirectional bit-addressable with internal pullups
P3.0~P3.7: Port 3, bidirectional bit-addressable with internal pullups
Alternative Functions of Port 3
PSEN: Program Store Enable, read strobe for external program memory
ALE: Address Latch Enable, for multiplexing AD0~AD7
A8~A15(P2.0~P2.7): high-byte address bus for external addressing
AD0~AD7(P0.0~P0.7): multiplexed low-byte address bus and data bus for external addressing