instrumentation for scientists

10 April 2008 (c) Paul Main

Instrumentation for Scientists• 640251 - Geoff Taylor and Paul Main• Brief History• Bipolar and MOSFET transistors• Digital Logic Primer• Logic Levels, Gates, Truth Tables• Decimal, Hexadecimal, Binary Arithmetic• Electronic Schematic Symbols & Logic• Lectures 10-12


A Short History of Computers

• The Abacus “Computing Tray” The first mechanical calculating machine. 28?


Computing Tray

• Used by Babylonian priests to keep track of their vast storehouses of grain. Still in use today. Circa 3000BC.

• In Roman times the board was given grooves to facilitate moving the counters in the proper files.

• Circa 1300BC Wire & Bead Abacus replaced the Chinese calculating rods.


Computing Tray

• A modern equivalent is an Accumulator or Register: used to accumulate results of arithmetic sums.

• Uses electronic (voltage) representation of binary numbers


John Napier• 1612 John Napier uses the printed decimal

point, devised logarithms and used numbered sticks - Napiers Bones - for calculating.


New Improved Abacus

• 1642AD: Blaise Pascal Invented the first mechanical calculator constructed of 10 toothed gears, wheels & teeth called “Pascalene”.

• The same principle was in use in automobile’s odometer mechanism

• Same principle is the basis for all mechanical calculators.


Joseph Marie Jacquard

• 1801: A linked sequence of punched cards programmed Jacquard’s loom to produce intricate weaving patterns in cloth.


By Royal Commission

• 1823: The royal Astronomical Society of Great Britain commissioned Charles Babbage to produce a programmable calculating machine. He was aided by Augusta Ada Byron, the countess of Lovelace. The machine was to produce navigational tables for the Royal Navy.


Babage’s Analytical Engine

1834 Babbage shifted his focus to work on The Analytical Engine. The mechanical computer stored 1000 20-digit decimal numbers and a variable program that could modify the function of the machine to perform various tasks.


Babbage IO devices

• Input to his engine was through punched cards (similar to punched cards of the 1950s-80s).

• It is assumed that he obtained the idea from Frenchman, Joseph Jaquard, who used punched cards as input to a weaving machine that he invented in 1801.


Dreams Faded

• After many years of work, Babage’s dream faded when he realised that the machinists of the day were unable to create the parts needed to complete his work.

• The analytical engine required 50 000 precision machined parts to allow his engine to function reliably.


Michael Faraday• Son of a Blacksmith, had limited formal

education but attended public lectures and became an avid reader

• 1813 Started working life at the London Royal Institution as a laboratory assistant

• 1821 demonstrated the electric motor effect.• 1831 demonstrated EMF(current) induced

by motion of magnet by a nearby conductor.


Electric Motors

• Electric Motors became available.

• Motor driven adding machines based on mechanical calculators developed by Blaise Pascal became popular.

• Electrically driven mechanical calculators were common office equipment until 1970s.

• 1844 - Samuel Morse sent a telegraph from Washington to Baltimore.


George Boole

• Publishes “Laws of Thought”, describing a system for symbolic & logical reasoning which becomes the basis for computer design.

• 1858 A telegraph cable spans the Atlantic Ocean & provides service for a few days.

• 1876 Alexander Graham Bell invents, and patents, the telephone.


William Shockley

• 1939 William Shockley observed P- and N- type regions in Silicon. Shockley forecast that a semiconductor amplifier was possible.

• WWII interrupted further work.• 1945: John von Neumann described the general-

purpose, stored program computer.• 1948: The invention of the Germanium bipolar

junction transistor at Bell Labs, by William Shockley, John Bardeen & Walter Brittain


First Electronic Computer• June 1943: Alan Turing, Tommy Flowers &

MHA Newman made operational the first electronic computer, Colossus

• Colossus was utilised to break the cipher codes generated by the mechanical Enigma Machine; German military communication was compromised.

• British cm wavelength radar assisted to provide military superiority.


The first point contact transistor


The first IC

• TI commercialised the Transistor.

• In 1958 Jack Kilby at TI realised that - Resistors formed by cutting small bars of silicon, Capacitors formed by wafers metalised on both sides, and silicon transistors could all be made on the same material.

• In september 1958 he created a phase-shift oscillator - the first IC on one wafer.


Intel 4004

• Intel went ahead with a general purpose logic chip capable of being programmed for instructions.

• First use of ‘Intelligence’ programmed by software. Bought the design back from Busicom.

• After 9 months development Intel’s first microprocessor is born, the 4004.


4004

November 197110 Micron technology2300 Transistors108 KHz Clock60 000 Instructions/secondBus width 4 bits640 bytes addressable12 Volt. Weighed < 1 Oz. P-channel MOSFETApplications: busicom calc


8008April 197210 Micron technology3500 Transistors200 KHz Clock0.06 Million Instructions Per Second (MIPS)Bus width 8 bits12 VoltAddress: 16 KbytesApps: Terminals, Calculators, Bottling Machines


8080April 19746 Micron Technology4 500 transistors

2 MHz Clock 0.64 MIPSBus width: 8 bits

12 Volt Addressable memory: 64 KbytesApps: Traffic light controller,

Altair computer (first PC)Performance = 10 x 8008


8085

• March 1976Clock speed: 5 MHz0.37 MIPSNumber of transistors: 6,500 (3 microns)8 bit data bus, 16 bit address bus.Typical use: Toledo scale. From measured weight and price the scale computed cost.Single 5 volt power supply


8086 (8088)June 1978/1979

3 Micron Technology

5, 8 &10 MHz clock

0.33, 0.66 & 0.75 MIPS

29 000 Transistors

16/8 bit data bus20 bit address bus (1MB)

5 Volt apps: IBM PCs & Clones

performance = 10 x 8080

Segmented architecture, CISC


IBMPC• 1981 The open-architecture IBM PC is launched

based on the Intel 8086

• 1980 PCDOS sold to IBM

• 1980 Ada emerged

• 1980 dBaseII popular

• 1982 First Clone PC

• 1982 AutoCAD

• 1983 TCP/IP


80186 (80188)

• 1982 Original NMOS 80186

• 1987 80C186 converted to CMOS - uses 1/4 power at twice clock rate

• Used in Controllers

• Still popular

• Segmented architecture

• Software Backward Compatible with 8086


80286February 19826 MHz -12 MHz clock0.9 - 2.66 MIPS

1.5 micron technology134 000 Transistors

16 bit data bus16MB Physical, 1GB Virtual

Performance =3 to 6 x 8086

Software Backward Compatible with 8086

Also V.20, AMD Cyrix etc


80386October 17, 198516 MHz - 33MHz

5 to 11 MIPS1 Micron technology

275 000 Transistors Data Bus width: 32 bitsAddressable memory: 4 gigabytesVirtual memory: 64 terabytesSoftware Compatible with 8086

32 bit “Flat Mode” available


80486DXApril 1989 25 MHz, 20 MIPS June 1991 50 MHz, 41 MIPS

1.2 Million Transistors

1-0.8 Micron TechnologyBus width: 32 bitsAddressable memory: 4 GBVirtual memory: 64 TB50X performance of the 8086.Software Compatible with 8086

486DX first CPU to include floating point maths co-processor.


80486DX2 & DX4 - Overdrive2 or 3 times overclocked cpu core, with standard memory transfer rate.

Plugged directly into a 486SX or 486DX socket and acted as a double or triple-clocked CPU.

Eg a 33MHz cpu replaced with an DX4 processor would use a memory transfer rate of 33MHz, and an internal clock rate of 99MHz.


PentiumMarch 1993

60 MHz 100 MIPS66 MHz 112 MIPS

3.1 million transistors

0.8 Micron technology

64 bit external data bus 32-bit microprocessor

32 bit address bus4 GB physical64 TB virtual

Software Compatible with 8086. BiCMOS


Pentium ProNovember 1995150-200 MHz5.5 million transistors

0.35 micron technology

64 bits front side bus

64 bits to L2 cacheAddressable memory: 64 gigabytesVirtual memory: 64 terabytes256K - 1MB L2 Cache

Software Compatible with 8086


NPN transistor cross-section

• IN IC form an NPN Bipolar Transistor is fabricated using a series of photolithographic and chemical processes.

• The base wafer is p-type silicon substrate around 0.25mm thick.• Boron is diffused to create a p type dopant, Phosphorous for n type.• The Yellow area is insulating SiO2. Orange – Aluminium conductors. • n+ indicates area of high conductivity & high phosphorous

concentration..


BIPOLAR JUNCTION TRANSISTORSchematic circuit symbols for NPN transistorB Base E EmitterC Collector


Bipolar Junction Transistor• Simple Circuit to illustrate BJT switching

for an NPN transistor


MOSFET• Metal Oxide Semiconductor Field Effect Transistor

• N Channel MOSFET schematic symbol:

• G Gate

• S Source

• D Drain


N CHANNEL MOSFET

IN IC form an NMOS Transistor is fabricated using a simpler series of photolithographic and chemical processes than the BJT. The resulting transistor area is also smaller.For an animation of device fabrication see: http://jas.eng.buffalo.edu/education/fab/NMOS/nmos.html


MOSFET

• The voltage on the gate-source causes an electric field across the Drain-Source channel

• Above a threshold voltage, Electrons are attracted into the channel causing a increase in Drain-Source conductance.

• In digital circuits we are only interested in the switching ability of transistors.

• A voltage Vgs > threshold voltage will switch the MOSFET ON – low drain-source resistance.

• Vgs < threshold will switvh the MOSFET OFF– high drain-source resistance.


MOSFET electrical properties

• N-MOS

• Behavior is

• Switch-like

• Vds fixed.


N-MOS test circuit

• N-MOS switching test circuit


Voltage vs 5V TTL Logic Levels

• True = Logic “1” = High Voltage Level

• False = Logic “0” = Low Voltage Level

• TTL “High” or “1” is 2.0V to 5V

• TTL “Low” or “0” is 0V to 0.8V.– Indeterminate Logic Level Between 0.8 & 2.0V– Actual Valid High & Low voltages vary

depending on the logic family & power supply voltage


Inverter

• Buffer - Logic state is Maintained

• Inverter - Logic state is Inverted - NOT


Inverter

• Complementary MOS (CMOS) Inverter


2-Input AND Logic Symbol

Truth Table for : 2-Input AND Gate

Output will be 1, only if all inputs are 1


3-Input AND Logic Symbols

Truth Table for : 3-Input AND Gate


AND Gate Equivalents

• AND Gates can be constructed using OR Gates & Inverters

• DeMorgans Theorum


NAND GATE


2-Input OR Logic Symbol• OR - True of any input is True -

– 2-Input OR Gate Truth Table


3-Input 0R Logic Symbol

• 3-Input OR Gate


Inverter Equivalents

• Inverters may be constructed from NAND gates or NOR gates with the inputs tied together


OR Gate Equivalents

• OR Gates can be constructed using AND Gates & Inverters


XOR Logic Symbol

• Exclusive OR - True if one input is True


XOR Gate

• XOR Gates can be constructed using AND gates, OR gates & Inverters


Logical Notation

• AND A AND B = A B = A & B

• OR A OR B = A + B = A | B

• NOT NOT A = A = A#

• XOR A XOR B = A B = A ^ B


Fundamental Data Types

Computers work in the binary number system.

The basic unit is the bit ("BInary digIT") A bit can be either 1 or 0

The other basic units are:Nybble 4 bits 0000 - 1111 (Binary), 0 - F (Hex)Byte 8 bits 0000 0000 - 1111 1111 (Binary),

00 - FF (Hex)Word 16 bits 0000 - FFFF (Hex)Longword 32 bits 0000 0000 - FFFF FFFF (Hex)Doubleword 64 bits 0000 0000 0000 0000 -

FFFF FFFF FFFF FFFF (Hex)


Hexadecimal, Binary & OctalOctalHexadecimalBinaryDecimal

00000001100011220010233001134401004550101566011067701117

108100081191001912A10101013B10111114C11001215D11011316E11101417F111115


Signed Number Representation

Hex numbers may be signed or unsigned.Unsigned numbers are positive only.

For 8 bits, they range from 0 .. 255 (0..FF hex)

Signed numbers are positive, negative or zero. The most significant bit is used to represent the sign of a number

For 8 bits, they range from -128 ..127 (80..7F hex)


Negative Number representation

Byte numeric representation (8 bits = 1 byte)

Signed Unsigned Binary Hexadecimal Octal+127 127 0111 1111 7F 177-128 128 1000 0000 80 200-4 252 1111 1100 FC 374-3 253 1111 1101 FD 375-2 254 1111 1110 FE 376-1 255 1111 1111 FF 377


Hex & Binary Notation

Hexadecimal numbers often have either a dollar sign '$‘ prefix or a ’0x' prefix as in “C”or a ‘H’ suffix (as in MASM/TASM) to indicate the number base is 16.


Binary Addition0 + 0 = 0, 0 + 1 = 1, 1 + 0 = 1,1 + 1 = 0, Carry 1


Binary Addition (1)

• Say for example we want to add two numbers, 5(dec) and 8(dec). Too easy!

• If we first convert these to binary we get 101(bin) and 1000(bin).

• Adding these together we get 1101(bin). • Converting back to decimal • 1101(bin)=23 + 22 + 0 + 20=8 + 4 + 0 + 1=13(dec)

• Simple - We knew that one!


Binary Addition (2)

• Say for example we want to add two numbers, 7(dec) and 9(dec).

• If we first convert these to binary we get 111(bin) and 1001(bin).

• Adding these together we get 10000(bin). • Converting back to decimal • 10000(bin) = 24 = 16(dec)

• Hmm! So many ones and zeroes!


Hexadecimal

• In Hexadecimal (Hex for short) we use the numbers 0..9 and A..F to represent groups of 4 bits.

• A group of four bits is called a nibble, and a group of 8 bits is called a byte.

• So any byte can be represented in 2 nibbles, or two hex digits.

• For example 11111110(binary) = 254(dec) = FE (hex)

• Now that’s easier to remember - FE FI FO FUM! And takes less letters than decimal!

• What interesting words can you make just using four hex digits?


Claude Shannon

• Interests: Model Planes, Radio Controlled boats, local telegraph, juggling, unicycling, and chess…

• Studied Boole’s work on Boolean Algebra

• Graduated with degrees in Electrical Engineering and Mathematics.

• Utilised and extended boolean algebra to operate on relays

• AND Invented the base 2 adder!• He also contributed to cryptography theory!


Full Adder (1)

• Full Adder Truth Table

Who invented the base 2 adder?


Full Adder (2)

• A Full Adder adds two bits, A0 & B0, plus the Carry-In as shown creating a Bit 0 Sum and Carry Out.

Carry

In

Carry Out

Bit 0 Sum


8 Bit Adder• 8 Full adders can be cascaded to

form an 8-bit ADDer

• The AVR assembly language instructions “ADD” and “ADC” configures the ALU to use the logic shown.

• Carry in is set to 0 for ADD.

• Carry in is set to CF for ADC.


One's complementInvert bits - The NOT operation is performed

invert 1101 0101 -> 0010 1010


Two's complementTake one's complement of a number and add 1

convert from positive to negative numberconvert from negative to positive number

Example:

Negate 1101 0101

-> 0010 1010 + 0000 0001

= 0010 1011


Two's complement1) Start with 0000 0011One's complement 1111 1100

Add 1 1111 1101

2) Start with 0000 0000 One's complement 1111 1111

Add 1 0000 0000


Equivalent Circuits• To make a TTL inverter requires a single

NPN transistor, diode and 2 resistors.• To make a simple Diode-Nor gate requires a

single transistor, 2 diodes and 3 resistors.• It is possible to create AND gates using NOR

gates and Inverters. (deMorgans theorum)• Example Inverting the inputs to a NAND gate -> OR gate.

• Work Example - OR, AND, MUX, Latch


Terminology - Edge transitions

• Logic “1” -> Logic “0” = Falling Edge

• Logic “0” -> Logic “1” = Rising Edge


Memory Elements: 1 Bit Latch

• Latches can be created using NAND Gates


Registers

• A register can be created using an array of latches with their gates connected together..

• The lower nibble of R01 R01.0..R01.3 can be created using the latches as shown here.


AVR Core Architecture


AVR Register Set (1)

• The AVR contains 32 General Purpose working registers - “Accumulators”

• The ALU supports 8 & 16 bit operations.



• The AVR contains 32 General Purpose working registers.

• Most instructions have full access to all the registers for 8 or 16 bit operations.

• The X, Y and Z registers have a special function. They can be set to index anywhere in memory, including any register as they are also mapped into memory.

• I.e. X, Y and Z they can be used as pointers.


The status register

• In computer code we may wish to test if variables A and B are equal.

• IF A=B, this means A – B = 0.• So the compiler creates code to load registers with

the values of variables A and B, perform subtraction.

• If the result is Zero the “Zero flag” is set.• Most computers can branch based on a “Zero flag”.


Status Register

Example “C” CodeIf (A == B) { // A EQUALS B i++; } else { // A NOT EQUAL B

}Assume variables A, B and i

are of type char (1 byte).

Equivalent Assembly Code

LD R0, A ; A -> R0

LD R1, B ; B -> R1

SUB R0, R1 ; SUBTRACT B-A

BNEQ ABNEQUAL ; SKIP if not eq.

LD R0, I ; i++;

INC R0

ST R0, I

ABNEQUAL:


Condition Codes Register: ZERO FLAG


AVR Status Register

• Bit#7 - Interrupt - Cleared on interrupt• 6 - T - biT for Bit Load & Store instructions• 5 - H - Half Carry

• 4 - S - Sign• 3 - V - oVerflow• 2 - N - Negative• 1 - Z - Zero• 0 - C - Carry• From Pages 9 & 10 of ATMEGA128 manual


Multiplexor - Data Selector

• Multiplex (MUX) many inputs to one output

• Switch selects the one signal source from many input signals.

• Like Stereo HiFi source selection switch


Two Input Multiplexor

Output = (Input0 & Select#)

| (Input1 & Select)

Two Input MuxTruth Table

OutputSelectInput 00Input 11


Four Input Multiplexor4 Input MultiplexorTruth TableSelect Line:

Output01Input 000Input 110Input 201Input 311


Eight Input Multiplexor

Eight Input MultiplexorTruth Table

OutputSelect Line:012

Input 0000Input 1100Input 2010Input 3110Input 4001Input 5101Input 6011Input 7111


74F151 8-Input MUX


74F151 8-Input MUX

Pin Names and Loading / Fanout


Mux vs DeMux


74LS138 8-Output DEMUXDe-Multiplex one input to many outputs -Reverse operation of a multiplexor74LS138 Truth Table


DeMultiplexor• The 74LS138 can be

implemented by the logic shown.

• The 54LS138 is identical in function, but can operate over the “Mil-spec” -55°C to 125°C Temperature Range.

• The 74LS138 can operate over the Commercial 0°C - 70°C Temperature Range.


ASCII & Extended IBM Graphics Character Set

00102030405060708090A0B0C0D0E0F0

0123456789ABCDEF


Acknowledgments & References• Altium Protel 98, DXP or Altium 6 to create these schematic

diagrams and timing diagrams.

• Logic Timing Diagrams are from Texas Instruments (TI) Logic Selection Guide - Digital Design Seminar

• National Semiconductor data sheets 74LS138.

• http://www.sea.vg/mic/2007/Atmel/Atmega128ManualDoc2467.pdf

• IEEE timeline of Computing

• Interfacing Sensors to the IBM PC.Tompkins & Webster

• Microelectronic Circuits - Sedra & Smith

• Paul Main AVR lecture notes - sea.net.au - October 2007

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