1. ECE 3430 – Intro to Microcomputer Systems
ECE 3430 – Introduction to Microcomputer Systems University of Colorado at Colorado Springs
Lecture #2
Agenda Today
1) Computer Hardware/Software
2) Operating Systems
3) HC11 Hardware Block Diagram
4) Peripheral Interfacing Techniques (Lab Breadboard Layout)
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

2. Computer Hardware/Software
All microprocessors and microcontrollers employ both hardware (HW)
and software (SW) to get things done.
Computer Hardware
circuitry
executes program instructions
handles input & output devices
has memory to load/store programs/data
CPU “Central Processing Unit” contains: Registers - Storage locations within the CPU. Faster than memory, used
to hold data and/or memory addresses during
execution of an instruction.
Arithmetic Logic Unit - (ALU) Circuitry that performs numerical
calculations and logic functions.
Control Unit - State Machine that decodes program instructions and controls
the execution of the instructions. Also allocates HW resources
within the CPU.
Why software?
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

3. Computer Hardware/Software
Typical Computer System
X-bit processor
processor capable of manipulating X-bits in 1 operation
Abbreviations
Microprocessor = uP
Microcontroller = uC
Non Volatile Memory
(program memory, ROM, Disk, CD)
CPU
- ALU
- Control Unit
- Registers
Volatile Memory
(data memory, RAM)
I/O
(Input/Output, Keyboard, Display)
Program memory typically non-volatile in uC systems. BIOS is non-volatile in uP systems.
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

4. Computer Hardware/Software
Limits of a uP - requires external memory - cannot directly interface to I/O devices, needs other integrated circuits (ICs)
- needs glue logic to interface to external memory and peripheral ICs
Benefits of uC - combines all needed circuitry on one IC - CPU, memory, I/O interface, glue logic
Types of Memory
RAM - Random Access Memory, volatile (loses contents when power is lost),
by convention is read/write
ROM - Read-Only Memory (still randomly accessible), non-volatile, keeps data when
power is removed
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

5. Computer Hardware/Software
RAM:
SRAM - Static RAM, faster more expensive, 4-6 transistors per memory cell DRAM - Dynamic RAM, slower, cheaper, needs special refresh circuitry
to maintain memory contents, 1 transistor per memory cell
ROM:
MROM (or just ROM) - Masked Programmed ROM, uses metal layers in
fab to write (cannot ever be changed) PROM - Programmable ROM, user can program electrically, fuse based, one-shot EPROM - Electrically Programmable ROM, user can program electrically but
cannot erase electrically, shine UV light through window on top of
chip to erase, long erase time (15-20 minutes) EEPROM - Electrically Erasable Programmable ROM, user can electrically
erase and reprogram the memory, high voltage (can erase individual bytes) FLASH EEPROM - new EEPROM technology, erased and programmed “in system”,
normal voltage (cheaper than EEPROMs – erase in sectors)
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

6. Traditional EEPROM vs. Flash EEPROM
Traditional EEPROMs have a larger cell size than Flash EEPROMs—so for a given amount of silicon, you get more memory with Flash than Traditional.
Write time for Flash is faster than Traditional—but erase time is faster for Traditional.
Traditional EEPROMs use Fowler-Nordheim tunneling to erase and write new data (this requires higher voltages).
Flash EEPROMs use Fowler-Nordheim tunneling to erase only and hot electron injection to write new data. Oscillators and a charge-pump can be used to generate the higher voltage on-chip.
Traditional EEPROMs can erase a single byte—while Flash EEPROMs erase sectors (maybe the whole chip).
Flash EEPROMs will typically wear out quicker than Traditional EEPROMs (10,000 erase/write cycles vs. 100,000 erase/write cycles).
Read access time for Traditional EEPROMs is faster than Flash EEPROMs.
Read and write access time for RAM is faster than all EEPROM technologies (at least the write time is)!
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

7. Computer Hardware/Software
Hardware Execution of Software
1) A program is written and inserted into memory. 2) The CPU initializes and sets up an internal register (called a program counter) to
point to the first instruction the CPU is to execute.
3) The CPU with “fetch” an instruction from the memory address that the program
counter points to.
4) The Control Unit decodes the instruction.
5) The Control Unit tells the ALU to perform an operation using the internal
registers.
6) The program counter increments to the next instruction.
Mention BIOS and reset vectors.
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

8. Computer Hardware/Software
Software Terminology:
Program - A set of instructions that the computer HW can execute.
Stored in memory as binary #’s.
Machine Code - The binary #’s representing the program (ex, A+B = ).
Instruction - Each CPU has a set of instructions that it knows how to execute
(ADD, SUB, LOAD). The instruction set is specific to the hardware.
Assembly Language - It is very difficult to program in machine code. Assembly programming
simplifies this by giving each instruction a mnemonic representation (ex, $1B = Machine Code, ABA = Assembly Instruction).
Source Code - The file of assembly mnemonics that the programmer creates.
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

9. Computer Hardware/Software
Software Terminology (continued)…
Assembler - A program that translates the “source code” at the assembly level into
machine instructions.
Object Code - The output of the assembler.
Cross-Assembler - An assembler ran on one computer but generates machine code to
be executed on another computer (i.e., using a PC to assemble an
HC11 program).
Native Assembler - Assembler on the same machine the program will be executed on.
High Level Language - Makes programming more general, easier to read, can handle
larger programs (C/C++).
Compiler - Program that translates high-level source code into machine instructions.
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

10. ECE 3430 – Intro to Microcomputer Systems
Operating Systems
Operating systems (OS’s) can be thought of as programs which build a virtual environment in which other programs can be run.
Operating systems insulate programmers from hardware complexity and provide memory and I/O device management.
Operating systems use device drivers to communicate with specific hardware peripherals. Device drivers are either compiled into the operating system or plug into an existing operating system.
Between the operating system and its associated drivers, programmers can write application programs with ease.
Most modern operating systems work to maximize CPU throughput by creating a notion of concurrently running processes and threads.
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

11. ECE 3430 – Intro to Microcomputer Systems
Operating Systems
On most microcomputer systems, the basic input output system (BIOS) contains the first instruction executed by the processor. After various power-on operations, control is transferred to the operating system. Other programs run on behalf of the OS.
Microcomputer systems are not required to run an operating system. Microprocessor-based systems almost always use operating systems—while microcontroller-based systems usually don’t.
Operating systems give life to the terms multiprocessing, multitasking, process, thread, et cetera.
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

12. ECE 3430 – Intro to Microcomputer Systems
Operating Systems
Example operating systems:
Microsoft DOS, Windows 95, 98, ME, NT, 2000, XP, Vista, CE…
Early versions of Windows (pre-95) we not operating systems—but rather graphical shells that ran on DOS technology.
Windows 2000, XP, and Vista are later versions of Windows NT technology (NT 5.0, 5.1, and 6.0 respectively).
UNIX (lots of variants: BSD, HP-UX, Sun Solaris)
Linux (lots of variants: Debian, Red Hat, Mandrake, SuSE)
Apple Mac OS (“Classic”, Mac OS X)
IBM OS/2 Warp
Operating systems are designed to support certain processor and hardware architectures.
We are not using an operating system to control the HC11 in lab. You will write the first instruction executed by the HC11.
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

13. ECE 3430 – Intro to Microcomputer Systems
HC11 Block Diagram
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

14. Peripheral Interfacing
Peripherals are input or output devices that interface to a microcomputer system.
Input devices: sensors
Mice
Keyboards
Toggle switches
Pushbuttons
Thermocouples
Output devices: actuators
Monitors/Liquid Crystal Displays (LCD)
Light-Emitting Diodes (LEDs)
Buzzers
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

15. Peripheral Interfacing
Active-High Sensor Interfacing:
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

16. Peripheral Interfacing
Active-Low Sensor Interfacing:
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

17. Peripheral Interfacing
Active-High Actuator Interfacing:
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

18. Peripheral Interfacing
Active-Low Actuator Interfacing:
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009

19. Lab Circuit (Breadboard)
Lecture #2
ECE 3430 – Intro to Microcomputer Systems
Fall 2009