Study sheet: Microprocessor Systems Architecture

📋 Course Outline

1. Computing and Microprocessor Foundations
2. Binary and Hexadecimal Representation
3. Von Neumann System Architecture
4. Buses and Address Decoding
5. Memory Organization and Operations
6. Memory Characteristics and Access
7. RAM Technologies
8. ROM Technologies
9. Memory Hierarchy and Selection

📖 1. Computing and Microprocessor Foundations

🔑 Key Concepts & Definitions

• Computer science : the science of processing information and combines information with automation
• Microprocessor : a complex integrated circuit that combines combinational and sequential logic and interprets and executes program instructions

★ Must-know

📌 Hardware is the concrete part of a computer system, whereas software is a set of program instructions stored in memory that defines the actions performed by the hardware.

• Intel created the first microprocessor, the 4-bit 4004, in 1971; it operated at 108 kHz and integrated approximately 2,300 transistors.

Further detail

• The transistor appeared in 1947, and Texas Instruments produced the first integrated circuit in 1958.

💡 Memory Hook

Transistor → integrated circuit → microprocessor

📖 2. Binary and Hexadecimal Representation

🔑 Key Concepts & Definitions

• Bit : the elementary binary information unit that can take the value 0 or 1
• Byte : a word made up of 8 bits

★ Must-know

📐 Formula — The binary number $(101)_2$ equals $1\times2^2+0\times2^1+1\times2^0=(5)_{10}$.

📐 Formula — The hexadecimal number $(9A)_{16}$ equals $9\times16^1+10\times16^0=(154)_{10}$.

Further detail

• The hexadecimal system uses the sixteen symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F.

💡 Memory Hook

Binary uses powers of 2, hexadecimal uses powers of 16

📖 3. Von Neumann System Architecture

🔑 Key Concepts & Definitions

• Von Neumann model : a universal machine architecture for programmed information processing proposed by John von Neumann in 1946

★ Must-know

• A basic von Neumann system contains:

  • a central processing unit
  • a main memory
  • input/output interfaces

• The microprocessor interprets and executes instructions, reads or saves results in memory, and communicates with exchange units under the timing of a clock.

Further detail

• A microprocessor is characterized by:
  • its clock frequency in MHz or GHz
  • its instruction rate in MIPS
  • the size of its data in bits

💡 Memory Hook

CPU–Memory–I/O connected by buses

📖 4. Buses and Address Decoding

🔑 Key Concepts & Definitions

• Bus : a set of wires that transmits the same type of information between components
• Data bus : bidirectional and transfers information between the microprocessor and its environment in both directions
• Address bus : The address bus is unidirectional and selects information in an address space containing up to $2^n$ locations, where n is the number of address conductors.
• Control bus : contains several conductors that synchronize information flows on the data and address buses

📝 Essential Points

• Address decoding assigns each peripheral an address zone and selects only one component at a time to prevent conflicts on the shared data bus.

💡 Memory Hook

Data bus transfers, address bus selects, control bus synchronizes

📖 5. Memory Organization and Operations

🔑 Key Concepts & Definitions

• Memory : a semiconductor circuit that records, retains, and restores information such as instructions and variables

★ Must-know

• With an address of n bits, a memory can reference at most $2^n$ memory locations, and each location contains one data word.

• 🔄 A memory cycle consists of:

  1. selecting the address
  2. choosing the operation
  3. selecting the memory
  4. reading or writing the data

Further detail

• A memory circuit has:
  • address inputs
  • data inputs
  • data outputs
  • a read/write control input
  • a chip-select input

💡 Memory Hook

Address → operation → chip select → data transfer

📖 6. Memory Characteristics and Access

🔑 Key Concepts & Definitions

• Memory capacity : the total number of bits stored in a memory and is often expressed in bytes
• Volatility : Volatility describes whether stored information is lost or altered when electrical power fails; volatile memory loses information, whereas non-volatile memory preserves it.

📝 Essential Points

• Memory access time is the interval between launching a read or write operation and the availability of the first information on the data bus.

📌 Random access reaches any known address in an address-independent time, whereas sequential access requires searching through preceding information and has a position-dependent access time.

💡 Memory Hook

Random access is address-independent; sequential access depends on position

📖 7. RAM Technologies

★ Must-know

📌 RAM provides temporary storage and is generally volatile, whereas ROM provides permanent non-volatile storage.

📌 SRAM stores each bit in a bistable circuit containing four to six transistors, whereas DRAM stores each bit as an electrical charge in a capacitor.

• DRAM must be refreshed regularly because leakage currents discharge its capacitor, and each destructive read must be followed by a rewrite.

📌 DRAM offers greater density and lower cost per bit for main memory, whereas faster SRAM is used for small memories such as caches and registers.

Further detail

• SDRAM synchronizes memory operations with a clock, while DDR-SDRAM transfers data on both the rising and falling edges of the clock.

💡 Memory Hook

SRAM is faster; DRAM is denser and cheaper

📖 8. ROM Technologies

🔑 Key Concepts & Definitions

• EPROM : a programmable ROM that can be erased by ultraviolet radiation and reprogrammed more than a thousand times
• EEPROM : a programmable and electrically erasable memory that can be programmed in situ and erased word by word

★ Must-know

📌 ROM is programmed by the manufacturer and cannot be modified by the user, whereas PROM can be programmed once by the user.

📌 Flash NOR permits random access and byte-by-byte programming, whereas Flash NAND provides sequential access and sector-based programming.

Further detail

• NAND Flash cells are approximately 40% smaller than NOR Flash cells, allowing higher integration density.

💡 Memory Hook

ROM → PROM → EPROM → EEPROM → Flash

📖 9. Memory Hierarchy and Selection

🔑 Key Concepts & Definitions

• Cache memory : a small, fast memory that accelerates access to main memory by storing the most frequently used data
• Mass storage : a large-capacity peripheral memory used for permanent storage or backup on magnetic or optical media

📝 Essential Points

• The main memory-selection criteria are:

  • capacity
  • speed
  • power consumption
  • cost

• Memory hierarchy balances performance and cost by placing frequently used information in small, fast memories and less-used information in larger, slower memories.

• The hierarchy from the processor outward is:

  • registers
  • cache memory
  • main memory
  • backing memory
  • mass storage

💡 Memory Hook

Greater capacity and lower cost → slower access farther from the processor

📊 Synthesis Tables

RAM and ROM Comparison

Memory type	Volatility	Main property	Typical use
SRAM	Generally volatile	Very fast	Caches and registers
DRAM	Generally volatile	High density and low cost	Main memory
ROM	Non-volatile	Permanent manufacturer programming	Fixed programs
EPROM/EEPROM/Flash	Non-volatile	Programmable and erasable	Reprogrammable storage

Flash NOR and NAND

Feature	NOR Flash	NAND Flash
Access	Random	Sequential
Programming	Byte by byte	By sector
Density	Lower	Higher
Interface	Dedicated address and data buses	Indirect input/output interface