INTRODUCTION TO 8051 MICROCONTROLLER
A brief INTRODUCTION TO 8051 MICROCONTROLLER
WHAT IS A MICROCONTROLLER?
All of the components needed for a controller were built right onto one chip.Thus A one chip computer, or microcontroller was born.A microcontroller is a highly integrated chip which includes, on one chip, all or most of the parts needed for a controller.The microcontroller could be called a “one-chip solution”.
Features of 8051 MICROCONTROLLER
The Intel 8051 is used in embedded systems
- 8-bit CPU
- 4k bytes ROM for the program
- 128 BYTES of RAM for variables
- 32 I/O lines ( 4 PORTS WITH 8 EACH )
- 2 timers
- 1 Serial port
- 6 interrupt
Block Diagram of 8051 MICROCONTROLLER
Pin Diagram of 8051 MICROCONTROLLER
IMPORTANT PINS of 8051 MICROCONTROLLER
Program Store Enable, the read signal for external program memory (active low).
Address Latch Enable, to latch address outputs at Port0 and Port2
External Access Enable, active low to access external program memory locations 0 to 4K
UART pins for serial I/O on Port 3
XTAL1 & XTAL2:
Crystal inputs for internal oscillator.
Vcc provides supply voltage to the chip. The voltage source is +5V.
Its ground pin.
XTAL1 and XTAL2pins 19,18
These 2 pins provide external clock. Way 1using a quartz crystal oscillator Way 2using a TTL oscillator
input pin and active high The high pulse must be high at least 2 machine cycles. power-on reset. Upon applying a high pulse to RST, the microcontroller will reset and all values in registers will be lost.
EA & PSEN
EApin 31External Access
There is no on-chip ROM in 8031 and 8032 . The EA pin is connected to GND to indicate the code is stored externally. PSEN ALE are used for external ROM. active low.
SENpin 29Program Store Enable
This is an output pin and is connected to the OE pin of the ROM.
ALEpin 30Address Latch Enable
It is an output pin and is active high.8051 port 0 provides both address and data.The ALE pin is used for de-multiplexing the address and data by connecting to the G pin of the 74LS373 latch.