ECE3120: Computer Systems

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ECE3120 Computer Systems

• Dr. Xubin He
• http//iweb.tntech.edu/hexb
• Email hexb_at_tntech.edu
• Tel [phone], Brown Hall 319

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• Today
• Basic Concepts
• Software

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Computer Concepts

• Computer
• Hardware
• Processor brain, CPU
• Datapath registers and ALU
• Control unit hardware instrucion logic.
• Memory place to store software programs and data
• I/O devices enter data/programs into the
  computer/display outputs
• Software programs
• A program is a set of instructions that the
  computer hardware can execute.

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Computer Organization
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Processor (Central Processing Unit)

• Datapath
• Register file a register is a storage location
  within the CPU.
• Arithmetic Logic Unit (ALU)perform all the
  arithmetic computations and logic evaluations.
• Control Unit
• Decodes and monitors the execution of
  instructions and coordinate the operations. The
  system clock synchronizes the activities of the
  CPU, which are measured by clock cycles. (GHz)
• Maintain 2 registers
• PC keeps track of the address of the next
  instruction to be executed
• Status Register flags the instruction execution
  result

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Microprocessor

• A processor implemented on a single integrated
  circuit (IC). Peripheral chips are needed to
  construct a product. A microcomputer is a
  computer that uses a microprocessor as its CPU
  (such as todays desktop).
• Classifications word length (number of bits that
  a microprocessor can manipulate in one
  operation).
• 4-bit (intel 4004,1971), 8-bit, 16-bit, 32-bit,
  64-bit.
• Limitations
• Requires external memory to execute programs
• Peripheral chips are needed to interface with I/O
  devices
• Glue logic (decoders, buffers) is needed to
  interconnect external memory and peripheral
  interface chips with the microprocessor.

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Microcontroller

• A computer implemented on a single VLSI chip. It
  contains everything a microprocessor contains
  plus some more components, such as
• Memory
• Timer
• ADC, DAC
• DMA controller
• parallel I/O interface (parallel ports)
• asynchronous serial I/O interface, synchronous
  serial I/O interface
• DSP features.

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Features of 68HCS12 microcontroller

• 16-bit CPU
• 64 KB memory space (also supports expanded memory
  up to 1 MB through a 16-KB window)
• 0 KB to 4KB of EEPROM
• 2 KB to 14 KB of on-chip SRAM
• 32 KB to 512 KB flash memory
• Sophisticated timer functions that include input
  capture, output compare, pulse accumulators,
  real-time interrupt, and COP timer
• Serial communication interfaces SCI, SPI, CAN,
  BDLC
• Background debug mode (BDM)
• 10-bit A/D converter
• Instructions for supporting fuzzy logic function

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Embedded Systems

• A product that uses one or more microcontrollers
  as controller (s). Also called embedded
  products.
• End users are interested in the functionality
  of the product, not the microcontroller itself.
• Cell phones, home security systems, and
  modern automobiles are examples of embedded
  products.

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Memory

• Semiconductor memory, magnetic, optical memory.
• Semiconductor memory
• Random access memory (RAM)volatile
• Dynamic RAM (DRAM) periodic refresh operations
  to maintain the stored information. Every a few
  milliseconds to over a hundred ms.
• Static RAM (SRAM)no need to refresh. More
  transistors are used to hold one bit information.
• Read-only memory (ROM) nonvolatile.
• MROM mask-programed ROM, programmed when being
  manufactured.
• PROM programmable ROM, one-time programmable ROM
  using PROM programmer/burner by end users.
• EPROM erasable PROM, strong ultraviolate
  light.erasable in bulk.
• EEPROM electrically EPROM, erased by elctrical
  signals and reprogrammed. Individual location.
• Flash memory take advantages of EPROM and EEPROM

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I/O devices

• Input device
• Allow users to enter data/programs into the
  computer so that computation can be performed.
• Examples
• Output device
• Display results of computation so that users can
  read them and equipment can be controlled.
• Examples

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Software

• Programs. A program is a set of instructions that
  can be executed by the computer hardware.
• Machine instructions
• A sequence of binary digits that can be executed
  by the processor
• e.g 0001100000000110 (Accumulator Alt--
  Accumulator AB)
• Hard to understand, program, and debug for human
  being
• Assembly language

Defined by assembly instructions An assembly
instruction is a mnemonic representation of a
machine instruction (e.g ABA) Assembly programs
must be translated before it can be executed
(assembler) Programmers need to work on the
program logic at a very low level and can achieve
high productivity.
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Assembly Language examples
line
addr.
machine code
source code
1 2 3 4 6
org 1000 ldaa 800 adda 801 adda 802 staa 900
end
1000 1003 1006 1009
00001000 B6 0800 BB 0801 BB 0802 7A 0900

• The programmer must be very familiar with the
  hardware organization of the microcontroller.
• Its difficult to understand for anyone other
  than the author
• Hard for large projects Work on a very low level.

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High-level languages

• - Syntax of a high-level language is similar to
  English, (C/C,Java,Fortran,PASCAL)
• - A translator is required to translate the
  program written in a
• high-level language -- done by a compiler
• - High-level languages allow the user to work on
  the program logic
• at higher level.

Source Code A program written in assembly or
high-level language Object Code The output of
an assembler or compiler