8051 block diagram

8051 block diagram and workig

1. 1
Microcontrollers

2. 2
Microcontroller:
•A smaller computer
•On-chip RAM, ROM, I/O ports...
•Example：Motorola’s 6811, Intel’s 8051, Zilog’s Z8X and PIC 16X
RAMROM
I/O
Port
Timer
Serial
COM
Port
Microcontroller
CPU
A single chip

3. 3
Microprocessor vs Microcontroller
Microprocessor
•CPU is stand-alone, RAM, ROM,
I/O, timer are separate
•designer can decide on the
amount of ROM, RAM and I/O
ports.
•expensive
•versatility
•general-purpose
Microcontroller
•CPU, RAM, ROM, I/O and timer
are all on a single chip
•fix amount of on-chip ROM, RAM,
I/O ports
•for applications in which cost,
power and space are critical
•single-purpose

4. 4
Microcontroller’s internal Blocks
•CPU ( ALU, Registers, Oscillator/clock, Bus control)
•RAM /Data memory
•ROM / program memory
•I/O ports
•Timer/counters
•Serial ports
•Interrupts

5. Microcontroller Block Diagram
CPU
On-chip
RAM
On-chip
ROM for
program
code
4 I/O Ports
Timer 0
Serial
PortOSC
Interrupt
Control
External interrupts
Timer 1
Timer/Counter
Bus
Control
TxD RxDP0 P1 P2 P3
Address/Data
Counter
Inputs

6. 6
Microcontroller Block Diagram
ALU
Internal ROM
I/O Ports
Internal RAM
Accumulator
Registers
Program Counter
Stack Pointer
Oscillator
Counter/Timer
Serial Port
Interrupt Logic
Bus Control

8. Program Counter and Data pointer
Program Counter (PC):
Program counter is a 16 bit Register. It holds the address of
the next instruction to be executed.
It does not have internal address (PC is the only register not
having the internal address)
Data Pointer (DPTR): DPH and DPL
DPTR is used to furnish memory address for internal and
external code access and external data access

9. A and B CPU Registers
•A and B registers are the two registers among the 34 general purpose registers
•Holds results of many instructions, particularly math and logical operations
•A register (Accumulator) is the most versatile and is used for many
operations including addition, subtraction, integer multiplication and division
and Boolean bit manipulations
•A register is also used for all data transfer between 8051 and any external
memory
•B register is used with A register for multiplication and division operations.

10. Flags and Program Status Word (PSW)

11. Special Function Registers

12. Special Function Registers-Continued

13. 8051 µC Hardware