Ece3430 Lecture 01

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Lecture #1 ECE 3430Intro to Microcomputer SystemsFall 2014

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ECE 3430Introduction to Microcomputer Systems

University of Colorado at Colorado Springs

Lecture #1

Agenda Today:

1) Microcomputers, Microprocessors, Microcontrollers

2) Number Systems

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Microcomputers and Terminology

There are lots of confusing terms floating around which dont alwayshave consistent definitions. Get used to it!

What is a microcomputer?

Term which evolved intopersonal computer (PC)desktopand

laptop. Sometimes just referred to as a computer.

A microcomputer is a computerbut a computer

is not a microcomputer.

Other types of computers (not digital in nature): Analog (slide ruler, abacus, mechanical computers)

Pulse (neural networks)

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Microcomputers and Terminology

Other types of digital computers: Minicomputers (larger than microcomputers)

Mainframe computers (larger than minicomputers)

Supercomputers (biggest and fastest)

Microcomputers have five classic components:

Input (keyboards, mice, touch-screens, etc.) Output (LCD panels, monitors, printers)

Memory (ROM, RAM, hard drives)

Datapath (performs arithmetic and logical operations [ALU])

Control (state machine in nature, controls the datapath)

The last two (datapath and control) are usually collectively

called theprocessoror central processor unit(CPU). Microcomputers are typically computers that are developed

around a microprocessor.

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Lecture #1 ECE 3430Intro to Microcomputer SystemsFall 2014 4

Microprocessors and Microcontrollers

Microprocessor:

A CPU packaged in a single integrated circuit.

Typically employs multiple execution pipelines, data and instruction

caches, and other complex logic to get very high execution

throughput (lots of work done in a given unit of time).

Microcontroller:

A computer system implemented on a single, very large-scale

integrated circuit. Generally speaking, a microcontroller contains

everything in a microprocessor plus on-chip peripheral devices(bells

and whistles). A microcontroller may contain memories, timer circuits,

A/D converters, USB interface engines, the kitchen

sink, et cetera.

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Number Systems

Number Base Notation Used in this Course:

Decimal, Base 10 or d

Ex) 11ord11

Binary, Base 2 0b orb orb

Ex) 0b1011orb1011or1011b

Octal, Base 8 q or q

Ex) q13or13q

Hexadecimal, Base 16 0x or h or h

Ex) 0xBDorhBDorBDh

ASCII or

Ex) Fred (non-terminated)orBarney (terminated)

The MSP430 assembler and C/C++ compiler will make use of one of the above. Well

discuss assembly, the assembler, and higher-level programming languages (C/C++)

later.

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Number Systems

Base ConversionBinary to Decimal Each digit has a weight of 2nthat depends on the position of the

digit.

Multiply each digit by its weight.

Sum the resultant products.

Ex) Convert b1011 to decimal

23 22 21 20 (weight)

% 1 0 1 1

= 1(23

) + 0(22

) + 1(21

) + 1(20

)= 1(8) + 0(4) + 1(2) + 1(1)

= 8 + 0 + 2 + 1= d11

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Number Systems

Base ConversionBinary to Decimal with Fractions The weight of the binary digits have negative positions.

ex) Convert b1011.101 to decimal

23 22 21 20 2-1 2-2 2-3

1 0 1 1 . 1 0 1

= 1(23) + 0(22) + 1(21) + 1(20) + 1(2-1) + 0(2-2) + 1(2-3)

= 1(8) + 0(4) + 1(2) + 1(1) + 1(0.5)+ 0(0.25)+ 1(0.125)

= 8 + 0 + 2 + 1 + 0.5 + 0 + 0.125= d11.625

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Number Systems

Base ConversionDecimal to Binary- the decimal number is divided by 2, the remainder is recorded- the quotient is then divided by 2, the remainder is recorded

- the process is repeated until the quotient is zero

ex) Convert 11 decimal to binary

Quotient Remainder2 11 5 1 LSB

2 5 2 1

2 2 1 0

2 1 0 1 MSB

= b1011

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Number Systems

Base ConversionDecimal to Binary with Fractions- the fraction is converted to binary separately- the fraction is multiplied by 2, the 0thdigit is recorded

- the remaining fraction is multiplied by 2, the 0thdigit is recorded

- the process is repeated until the fractional part is zero

ex) Convert 0.375 decimal to binary

Product 0thDigit

0.3752 0.75 0 MSB

0.752 1.50 1

0.52 1.00 1 LSB

d0.375 = b.011

finished

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Number Systems

Base ConversionHex to Decimal- the same process as binary to decimal except the weights are now BASE 16- NOTE (hA=d10, hB=d11, hC=d12, hD=d13, hE=d14, hF=d15)

ex) Convert h2BC to decimal

162 161 160 (weight)

2 B C

= 2(162) + B(161) + C(160)

= 2(256) + 11(16) + 12(1)

= 512 + 176 + 12= d700

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Number Systems

Base ConversionHex to Decimal with Fractions- the fractional digits have negative weights (BASE 16)- NOTE (hA=d10, hB=d11, hC=d12, hD=d13, hE=d14, hF=d15)

ex) Convert h2BC.F to decimal

162 161 160 16-1 (weight)

2 B C . F

= 2(162) + B(161) + C(160) + F(16-1)

= 2(256) + 11(16) + 12(1) + 15(0.0625)

= 512 + 176 + 12 + 0.938= d700.938

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Number Systems

Base ConversionDecimal to Hex

- the same procedure is used as before but with BASE 16 as the divisor/multiplier

ex) Convert 420.625 decimal to hex

1st, convert the integer part

Quotient Remainder

16 420 26 4 LSB

16 26 1 10

16 1 0 1 MSB

= h1A4

2nd, convert the fractional part

Product 0thDigit0.62516 10.00 10 MSB

= h.A

d420.625 = h1A4.A

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Number Systems

Base ConversionOctal to Decimal / Decimal to Octal

The same procedure is used as before but with BASE 8as the divisor/multiplier

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Number Systems (Shortcuts)

Base ConversionHex to BinaryEach HEX digit is made up of four binary bits which represent 8, 4, 2, and 1

Ex) Convert hABC to binary

A B C

= 1010 1011 1100

= b1010 1011 1100

Octal to Binary works the same except using groups of three binary

bits which represent 4, 2, and 1.

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Number Systems (Shortcuts)

Base ConversionBinary to Hex- every 4 binary bits for one HEX digit- begin the groups of four at the LSB

- if necessary, fill the leading bits with 0s

ex) Convert b1100101111 to hex

= 0011 0010 1111

3 2 F

= h32F

Binary to Octal works the same way using groups of 3 binary bits.

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Number Systems

Binary Addition- same as BASE 10 addition- need to keep track of the carry bit

ex) Add b1011 and b1001

1 1

1 0 1 11 0 0 1

+________

1 0 1 0 0

Carry Bit

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Number Systems

Ways to represent integer signed values: Sign-Magnitude (historical): b1111 1111 = d-127 0 and -0 can be represented.

8-bit range: -127 to 127

Number line: 0,1,,127,-0,-1,,-127

Ones Complement (historical): b1111 1111 = d-0

0 and -0 can be represented.

8-bit range: -127 to 127

Number line: 0,1,,127,-127,-126,,-0

Twos Complement (used today): b1111 1111 = d-1

Only one 0 representation.

Always one more negative value than positive. 8-bit range: -128 to 127

Number line: 0,1,,127,-128,-127,-1

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Number Systems

Twos Complement- this encoding was chosen to represent negative numbers in modern computers- this way we can use adding circuitry to perform subtraction (easily)

- since the number of bits we have is fixed (i.e., 8), we use the MSB as a signbit

Positive #s : MSB = 0 (ex: b0000 1111 is positive number)

Negative #s : MSB = 1 (ex: b1000 1111 is negative number)

- the range of #s that a twos complement code can represent is:

(-2n-1) < N < (2n-11) : n = number of bits

ex) What is the range of #s that an 8-bit twos complement code can represent?

(-28-1) < N < (28-11)

(-128) < N < (+127)

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Number Systems

Twos Complement Negation- to take the twos complement of a positive number (i.e., find its negative equivalent)

Nc = 2nN Nc= Twos Complement

N = Original Positive Number

ex) Find the 8-bit twos complement representation of 52dec

N = +52dec

Nc = 28 52 = 25652 = 204 = b1100 1100

Note the Sign Bit

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Number Systems

Twos Complement Negation (a second method)- to take the twos complement of a positive number (i.e., find its negative equivalent)

1) Invert all the bits of the original positive number (binary)

2) Add 1 to the result


N = +52dec = b0011 0100

Invert: = 1100 1011

Add 1 = 1100 1011

+ 1

--------------------

b1100 1100 (-52dec)

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Number Systems

Twos Complement Negation (a third method)

1. Begin with the original positive value.

2. Change all of bits to the left of the right-most 1 to the opposite state. Done.


N = +52dec = b0011 0100

right-most 1

b1100 1100 (-52dec)

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Number Systems

Twos Complement Addition

-Addition of twos complement numbers is performed just like

standard binary addition.

- However, the carry bit is ignored.

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Number Systems

Twos Complement Subtraction

- now we have a tool to do subtraction using the addition algorithm

ex) Subtract d8 from d15

d15 = b0000 1111

d8 = b0000 1000 -> twos complement -> invert 1111 0111

add1 1111 0111

+ 1

-----------------

1111 1000 = d-8

Now Add: 15 + (-8) = 0000 11111111 1000

+_________

1 0000 0111 = d7Disregard Carry

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Number Systems

Twos Complement Overflow

- If a twos complement subtraction results in a number that is outside

the range of representation (i.e., -128 < N < +127), an overflow

has occurred.

ex) -100dec100dec- = -200dec (cant represent)

- There are three cases when overflow occurs

1) Sum of like signs results in answer with opposite sign

2) NegativePositive = Positive

3) PositiveNegative = Negative

- Boolean logic can be used to detect these situations.

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Number Systems

Binary Coded Decimal- Sometimes we wish to represent an individual decimal digit as

a binary representation (i.e., 7-segment display to eliminate a decoder)

- We do this by using 4 binary digits.

Decimal BCD

0 00001 0001 ex) Represent 17dec2 00103 0011 Binary = 101114 0100 BCD = 0001 01115 01016 01107 01118 10009 1001

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Number Systems

ASCII

American Standard Code for Information Interchange.

English alphanumeric characters are represented with a 7-bit code.

ex) A = h41

a = h61

There are ASCII tables everywhere. Google it.

Unicode

Supports text expressed in most of the worlds writing systems.

Each character represented by one or more bytes. UTF-8, UTF-16 are most popular today.

UTF-8 is ubiquitous on the World-Wide Web (avoids complications arising from

byte-ordering).

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Ece3430 Lecture 01