Transcript Slide 1

The 8051 Microcontroller
Architecture
• A microcontroller (μC) is a single integrated circuit that executes a user
program for controlling some device.
• A microcontroller has a CPU in addition to a fixed amount of RAM, ROM, I/O
ports, serial port, and a timer all on a single chip.
• An embedded system uses a microcontroller to do one task and one task
only.
• Microcontrollers are found in devices such as microwave ovens, automobiles,
keyboards, CD players, cell phones, security systems, electronic toys, garage
door openers, answering machines, … etc.
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Differences between Microprocessors and
Microcontrollers
1. Microprocessors contain no
ROM, no RAM, no I/O ports,
while microcontrollers contain
ROM, RAM, I/O ports, timers
and other peripherals.
2. Microcontroller systems are
cheaper and more cost
effective.
3. The computing power of
microprocessors is higher.
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Factors Influencing the Selection of Microcontroller Chips
• Speed
• Packaging
• Power consumption
• Amount of RAM and ROM on-chip
• Number of I/O pins
• How easy to upgrade to higher performance versions
• Cost per unit
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Commercial 8-bit Microcontrollers
1. Intel’s 8051 Family
2. Microchip’s PIC Family
3. Motorola’s 6811 Family
4. Zilog’s Z8 Family
8051 Family Manufacturers
• Intel (Original)
• Atmel
• Philips/Signetics
• AMD
• Infenion (Formally Siemens)
• Dallas Semiconductors
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The 8051 Microcontroller
• 8-bit CPU
• 128B on-chip RAM
• 4KB on-chip ROM
• 2 Timers
• Four I/O Ports (Each 8-bits wide)
• One Serial Port
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DIP Package
SMD
Package
8051 Pin Configuration
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8051 Family Members
Microcontroller
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On-chip ROM
On-chip RAM
Timers
8051
4K ROM
128 bytes
2
8031
0
128 bytes
2
8751
4K EPROM
128 bytes
2
8951
4K Flash ROM
128 bytes
2
8052
8K ROM
256 bytes
3
8032
0
256 bytes
3
8752
8K EPROM
256 bytes
3
8952
8K Flash ROM
256 bytes
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8051 IC Minimum Connections
1 Machine Cycle = 12 Clock Periods = 12/ fck
fck = Clock frequency (4MHz – 30MHz)
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8051 Memory Architecture
• The 8051 microcontroller uses the Harvard Architecture
• In Harvard Model the program memory is separated from data memory
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Memory Organization
Internal and External Memories
Internal RAM Memory Map
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On-chip ROM Address Space
Code Memory
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Memory Expansion
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Special Function Registers (SFRs)
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The 8051 Basic Registers
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PSW Register (Flag Register)
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8051 I/O Ports
• The 8051 contains 4 I/O Ports
• Each port has 8-lines
• Each port can be programmed for input or
output of data
• Port 0 and Port 2 can be used data and
address lines for external memory interfacing
• Port 3 has alternate functions for external
connections
• Port 0 should be connected to pull-up resistors
before using it for data input or output
• Port 1 is solely designed for I/O data exchange
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