Tom Lenihan
Architecture Of A Single Board
Computer
Defining The Components of a
Computer
• What Elements Are Required?
– Electronic Integrated Circuits which are configure
together to form the Hardware Architecture of
the computer
– Software called the Operating System programme
and makes the computer function and interact
with the outside world
• Electronic Integrated Circuits
– These electronic circuits (collection of transistors)
come in varying sizes, densities and functionally.
– Small Scale Integration (SSI), Medium Scale
Integration (MSI), Large Scale Integration (LSI) and
Very Large Scale Integration (VLSI)
– VLSI would tend to be the domain for the central
core processor called a Micro Processor and
typically use 250 million to 1.5 billion transistors.
The semiconductor is etched up to an resolution of
25nM ie. 0.000’000’025 of a meter
• Software
– Software is any code or programme that can run on
a Computer (Micro Processor) and result in a
function for that processor.
– e.g. An Operating System such as Windows 7, Unix,
Sun OS, MacOS 10 etc.
– Computer Games, MicroSoft Office, iTunes etc., etc.
Computer Applications
• Computer Applications where older
mechanical mechanisms have been replaced.
– Domestic Appliances: such as Microwaves,
Cookers, Fridges, TV’s,…the list goes on….
– Transport: Cars, Aeroplanes, Trains etc.
– Industry: Robots, Automated Production Lines,…
– Communications: Mobile Phones, Satellites,…
– Commercial: Cash registers, ATM, Type Writers…
In Fact every facet of modern life has been
influenced by the computer.
Types of Computers
• There are basically 2 types of computer
General Purpose Computer such as the standard
Desktop PC, Laptop, Mainframe Computer which
can run general purpose application software
which is loaded up and run when required by an
operator.
Micro Controller which runs dedicated software for
a specific purpose such as controlling the engine
of a car, the flight of an aeroplane, the cycle of a
washing machine, etc….
The TomAL
Target Development System
PCB (Printed Circuit Board)
Overlay
Component Level Circuit Diagram
Intel 8085 Internal Diagram
INTR INTA RST5.5 RST6.5
RST7.5
TRAP
SID
INTERUPT CONTROL
SOD
SERIAL I/O CONTROL
8-BIT INTERNAL DATA BUS
ACCUMULATOR
(A REG) (8)
TEMP
REG
INSTRUCTION
REGISTER (8)
(8)
FLAG
FLIP-FLOPS
(5)
ARITHMETIC
LOGIC
UNIT
(ALU)
INSTRUCTION
DECODER
AND
MACHINE
CYCLE
ENCODER
TIMING AND CONTROL
CLK
GEN
CLK
OUT
CONTROL
READY
RD WR
STATUS
ALE
S0 S1 IO/M
DMA
HOLD HLDA
B REG (8)
C REG (8)
D REG (8)
E REG (8)
H REG (8)
L REG (8)
REGISTER
ARRAY
STACK POINTER (16)
PROGRAM COUNTER (16)
INCREMENT/DECREMENT
ADDRESS LATCH (16)
ADDRESS BUFFER
ADDRESS DATA BUFFER
A8 TO A15
ADDRESS BUS
AD0 TO AD7
DATA ADDRESS BUS
RESET
RESET RESET
IN
OUT