1. ECE 3430 – Intro to Microcomputer Systems
ECE 3430 – Introduction to Microcomputer Systems University of Colorado at Colorado Springs
Lecture #1
Agenda Today:
1) Microcomputers, Microprocessors, Microcontrollers
2) Number Systems
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

2. Microcomputers and Terminology
There are lots of confusing terms floating around which don’t always
have consistent definitions. Get used to it!
What is a microcomputer?
Term which evolved into personal computer (PC)—desktop and
laptop. Sometimes just referred to as a computer.
A microcomputer is a computer—but a computer
is not a microcomputer.
Other types of computers (not digital in nature):
Analog (slide ruler, abacus, mechanical computers)
Pulse (neural networks)
Talk about main components of a microcomputer.
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

3. 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 the processor or central processor unit (CPU).
Microcomputers are typically computers that are developed around a microprocessor.
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

4. Microprocessors and Microcontrollers
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.
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

5. Use Models for Microprocessors/Microcontrollers
Used in systems that need to do complex calculations (serious number
crunching).
Used in systems that need to do calculations very quickly.
Microcontrollers:
Typically don’t have overly-complex datapaths and control logic.
Microcontrollers typically live in a system to do one dedicated operation.
Circuits that do complex control operations (not complex calculations)
use microcontrollers.
The datapath complexity of a microprocessor is often scaled back in
microcontrollers—in favor of on-chip peripheral devices.
This course will focus on the use of the MSP430 microcontroller
to solve engineering problems (see chip timeline on web).
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

6. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Number Base Notation Used in this Course:
Decimal, Base 10 <num> or d’<num>’
Ex) 11 or d’11’
Binary, Base b<num> or b’<num>’ or <num>b
Ex) 0b1011 or b’1011’ or 1011b
Octal, Base 8 q’<num>’ or <num>q
Ex) q’13’ or 13q
Hexadecimal, Base 16 0x<num> or h’<num>’ or <num>h
Ex) 0xBD or h’BD’ or BDh
ASCII ‘<chars>’ or “<chars>”
Ex) ‘Fred’ (non-terminated) or “Barney” (terminated)
The MSP430 assembler and C/C++ compiler will make use of one of the above. We’ll
discuss assembly, the assembler, and higher-level programming languages (C/C++)
later.
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

7. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Base Conversion – Binary to Decimal
Each digit has a “weight” of 2n that depends on the position of the
digit.
Multiply each digit by its “weight”.
Sum the resultant products.
Ex) Convert b’1011’ to decimal
(weight) %
= 1•(23) + 0• (22) + 1• (21) + 1• (20) = 1•(8) + 0• (4) + 1• (2) + 1• (1) = = d’11’
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

8. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Base Conversion – Binary to Decimal with Fractions
The weight of the binary digits have negative positions. ex) Convert b’ ’ to decimal
= 1•(23) + 0• (22) + 1• (21) + 1• (20) + 1• (2-1) + 0• (2-2) • (2-3) = 1•(8) + 0• (4) • (2) • (1) • (0.5) + 0• (0.25) + 1• (0.125) = = d’11.625’
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

9. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Base Conversion – Decimal 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 Remainder LSB MSB = b’1011’
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

10. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Base Conversion – Decimal to Binary with Fractions - the fraction is converted to binary separately - the fraction is multiplied by 2, the 0th digit is recorded - the remaining fraction is multiplied by 2, the 0th digit is recorded - the process is repeated until the fractional part is zero ex) Convert decimal to binary Product th Digit • MSB • • LSB d’0.375’ = b’.011’
finished
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

11. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Base Conversion – Hex to Decimal - the same process as “binary to decimal” except the weights are now BASE NOTE (h’A’=d’10’, h’B’=d’11’, h’C’=d’12’, h’D’=d’13’, h’E’=d’14’, h’F’=d’15’) ex) Convert h’2BC’ to decimal (weight) B C = 2• (162) + B• (161) + C• (160) = 2•(256) • (16) • (1) = = d’700’
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

12. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Base Conversion – Hex to Decimal with Fractions - the fractional digits have negative weights (BASE 16) - NOTE (h’A’=d’10’, h’B’=d’11’, h’C’=d’12’, h’D’=d’13’, h’E’=d’14’, h’F’=d’15’) ex) Convert h’2BC.F’ to decimal (weight) B C F = 2• (162) + B• (161) + C• (160) + F• (16-1) = 2•(256) • (16) • (1) • (0.0625) = = d’ ’
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

13. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Base Conversion – Decimal to Hex - the same procedure is used as before but with BASE 16 as the divisor/multiplier ex) Convert decimal to hex st, convert the integer part… Quotient Remainder LSB MSB = h’1A4’
2nd, convert the fractional part… Product th Digit • MSB = h’.A’
d’ ’ = h’1A4.A’
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

14. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Base Conversion – Octal to Decimal / Decimal to Octal The same procedure is used as before but with BASE 8 as the divisor/multiplier
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

15. Number Systems (Shortcuts)
Base Conversion – Hex to Binary
Each HEX digit is made up of four binary bits which represent 8, 4, 2, and 1
Ex) Convert h’ABC’ to binary A B C
= = b’ ’
Octal to Binary works the same except using groups of three binary
bits which represent 4, 2, and 1.
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

16. Number Systems (Shortcuts)
Base Conversion – Binary 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 0’s ex) Convert b’ ’ to hex =
3 2 F
= h’32F’
Binary to Octal works the same way using groups of 3 binary bits.
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

17. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Binary Addition - same as BASE 10 addition - need to keep track of the carry bit ex) Add b’1011’ and b’1001’
+________ Carry Bit
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

18. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Ways to represent integer signed values:
Sign-Magnitude (historical): b’ ’ = d’-127’
0 and -0 can be represented.
8-bit range: to 127
Number line: 0,1,…,127,-0,-1,…,-127 <repeat>
One’s Complement (historical): b’ ’ = d’-0’
8-bit range: -127 to 127
Number line: 0,1,…,127,-127,-126,…,-0 <repeat>
Two’s Complement (used today): b’ ’ = 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 <repeat>
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

19. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Two’s 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 sign bit Positive #’s : MSB = 0 (ex: b’ ’ is positive number) Negative #’s : MSB = (ex: b’ ’ is negative number) the range of #’s that a two’s complement code can represent is: (-2n-1) < N < (2n-1 – 1) : n = number of bits
ex) What is the range of #’s that an 8-bit two’s complement code can represent?
(-28-1) < N < (28-1 – 1) (-128) < N < (+127)
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

20. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Two’s Complement Negation - to take the two’s complement of a positive number (i.e., find its negative equivalent) Nc = 2n – N Nc = Two’s Complement N = Original Positive Number
ex) Find the 8-bit two’s complement representation of –52dec
N = +52dec
Nc = 28 – 52 = 256 – 52 = 204 = b’ ’
Note the Sign Bit
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

21. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Two’s Complement Negation (a second method) - to take the two’s 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
ex) Find the 8-bit two’s complement representation of –52dec
N = +52dec = b’ ’
Invert: = Add 1 = b’ ’ (-52dec)
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

22. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Two’s Complement Negation (a third method)
Begin with the original positive value.
Change all of bits to the left of the right-most 1 to the opposite state. Done.
ex) Find the 8-bit two’s complement representation of –52dec
N = +52dec = b’ ’
right-most 1
b’ ’ (-52dec)
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

23. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Two’s Complement Addition Addition of two’s complement numbers is performed just like standard binary addition However, the carry bit is ignored.
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

24. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Two’s Complement Subtraction - now we have a tool to do subtraction using the addition algorithm ex) Subtract d’8’ from d’15’ d’15’ = b’ ’ d’8’ = b’ ’ -> two’s complement -> invert add = d’-8’ Now Add: (-8) = _________ = d’7’ Disregard Carry
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

25. ECE 3430 – Intro to Microcomputer Systems
Number Systems
Two’s Complement Overflow - If a two’s complement subtraction results in a number that is outside the range of representation (i.e., -128 < N < +127), an “overflow” has occurred. ex) -100dec – 100dec- = -200dec (can’t represent) - There are three cases when overflow occurs 1) Sum of like signs results in answer with opposite sign 2) Negative – Positive = Positive 3) Positive – Negative = Negative - Boolean logic can be used to detect these situations.
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

26. ECE 3430 – Intro to Microcomputer Systems
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 ex) Represent 17dec Binary = BCD =
Comment on why BCD exists:
* Simplifies some display electronics (simple mapping).
* Avoids conversions binary to ASCII.
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014

27. ECE 3430 – Intro to Microcomputer Systems
Number Systems
ASCII
American Standard Code for Information Interchange.
English alphanumeric characters are represented with a 7-bit code. ex) ‘A’ = h’41’ ‘a’ = h’61’
There are ASCII tables everywhere. Google it.
Unicode
Supports text expressed in most of the world’s 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).
Lecture #1
ECE 3430 – Intro to Microcomputer Systems
Fall 2014