Microcontrollers

1
Microcontrollers

• Introduction to Computing

2
Computer Organization

• Central Processing Unit (CPU)
• Microprocessor (uP)
• Microcontroller (uC)
• Memory
• ROM
• RAM
• Peripherals
• Printer
• Keyboard
• Monitor

3
Busses

• A related group of nodes (conductors)
• Address
• Unidirectional
• Data
• Bi-directional
• Control
• Rarely grouped

4
Binary Patterns

• Bit (1 or 0)
• Nibble (4 bits)
• Byte (8 bits)
• Word (16 bits is common but not standard)
• Kilobyte (210 or 102410 bytes)
• Megabyte (220 or 1 048 57610 bytes)
• Gigabyte (230 or 1 073 741 82410 bytes)

5
Memory Basics

• ROM Read Only Memory
• Permanent information
• Boot-up programs (diagnostics)
• Subroutines used by many applications
• Application memory if only one application
• Data memory if data set is constant

6
Memory Basics

• RAM Random Access Memory
• Better Name Read / Write memory
• Information can be changed
• Application memory if multiple applications
• Data memory if data must be changeable
• Faster operation

7
Buses Connect CPU and RAM
Data Bus
CPU
RAM
Address Bus
8
Buses connect the CPU with ROM
Data Bus
CPU
ROM
Address Bus
9
Application Memory
uC RAM
uP RAM Various Applications
uC ROM Single Application
uP ROM
Microprocessor Computers
Microcontroller Computers
(Embedded
System)
10
Fetch Execute Machine Cycle
Fetch Instruction
Execute Instruction
One machine cycle
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Program Counter

• 16 bit program (ROM) addresses only.
• After execution, PC always contains the address
  of the very NEXT instruction.
• Always contains 0000h at Reset.
• Largest ROM address is FFFFh.

12
Reset Vector

• Reset Vector (0000H) cannot be changed.
• At the Reset event, 0000H is automatically loaded
  into the program counter.
• The instruction stored at ROM 0000H is always
  executed at start-up.

13
Running a Program
PC 1400, ACC ?
PC 1402, ACC 21h
PC 1404, ACC 63h
PC 1406, ACC 75h
-2 is added to PC and the SJMP instruction
repeats itself
PC 1408, 1406
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8051 Series Microcontrollers

• Many varieties.
• On chip ROM
• On chip RAM
• I/O points
• Timers
• Interrupts
• Vcc
• Packages
• One instruction set