DIGI 1-59

• A processor is the logic circuitry that responds to and processes basic instructions that drive a computer
• The term "processor" has generally replaced the term central processing unit (CPU)
• The processor in a personal computer or embedded in small devices is often called a microprocessor
• The processor (CPU) is the computer's brain. it allows the processing of numeric data entered in binary form and the execution of instructions stored in memory.
• A microprocessor is used as the CPU in a microcomputer and is a program-controlled device that fetches, decodes, and executes instructions
• Most microprocessors are single-chip devices and are the backbone of a computer system, known as the CPU
• Microprocessor speed depends on the data bus width and is categorized by the number of bits their ALU can work with at a time
• The evolution of Intel microprocessors:

  • First generation (1939 – 1954): Vacuum Tubes
  • Second generation (1954 – 1959): Transistors
  • Third generation (1959 – 1971): Integrated Circuits (IC)
  • Fourth generation (1971 – Present): Microprocessors
• A bus connects all internal computer components to the CPU and main memory.

  Every bus has a clock speed measured in MHz. A fast bus allows data to be transferred faster, which makes applications run faster.
• Compiler: translates high-level language programs into machine code at once without requiring special instructions to store in memory
• Interpreter: translates source code into object code one instruction at a time. It is similar to a human translator translating what a person says into another language, sentence by sentence.
• RISC (Reduced Instruction Set Computer) - RISC microprocessors, or chips, take advantage of the fact that most of the instructions for computer processes are relatively simple and computers are designed to handle those simple instructions extremely quickly. RISC chips must break the complicated code down into simpler units before they can execute it.
• Features of RISC processors:

  • Use a small and limited number of instructions
  • Consume less power and have high performance
  • Each instruction is simple and consistent
  • Use simple addressing modes
  • Instructions are of uniform fixed length
• CISC (Complex Instruction Set Computer) chips have a large, complex resident instruction set, processing complex codes more quickly
• Features of CISC processors:

  • Have a large amount of different and complex instructions
  • Use complex addressing modes
  • Can execute different machine programs
  • Use micro-program control unit
  • Have a limited number of registers
• 8086 Microprocessor is divided into two functional units: Execution Unit (EU) and Bus Interface Unit (BIU)
• The system bus connects the CPU to the memory and input/output devices
• The control bus carries signals that control the action of the computer.
• The address bus carries the addresses from the processor to the main memory or other input/output devices.
• The CPU consists of registers, the arithmetic logic unit (ALU), and the control unit

  
• Registers are a type of computer memory used to quickly accept, store, and transfer data and instructions that are being used immediately by the CPU.

  A register must be large enough to hold an instruction.
• The 8086 microprocessor is divided into two units: the Execution Unit (EU) and the Bus Interface Unit (BIU)
• The EU controls operations on data using the instruction decoder & ALU, while the BIU takes care of all data and address transfers on the buses for the EU
• BIU (Bus Interface Unit) takes care of all data and addresses transfers on the buses for the EU like sending addresses, fetching instructions from the memory, reading data from the ports and the memory as well as writing data to the ports and the memory.
• Registers in the 8086 microprocessor include the Segment register, AX & DX registers, BX register, CX register, and FLAGS
• Segment register holds addresses of instructions and data in memory.

  AX & DX registers are used for 8-bit multiplication.

  BX register specifies 16-bit effective address of a memory location.

  CX register is always used as the implied counter

  FLAGS record the condition of the microprocessor's calculation.
• Sequential logic circuits have inherent "Memory" and can be event-driven, clock-driven, or pulse-driven
• A transistor is a miniature semiconductor that regulates or controls current or voltage flow in addition amplifying and generating these electrical signals and acting as a switch/gate for them.
• An integrated circuit or monolithic integrated circuit is a set of electronic circuits on one small flat piece of semiconductor material, usually silicon.
• Every bus has a clock speed measured in MHz A fast bus allows data to be transferred faster, which makes applications run faster. 3 Main system bus (Control Bus, Address bus, Data Bus)
• Control Bus - carries signals that control the actions of the computer.
• Address bus - carries the address from the processor to main memory or other memory I/O devices. it is one direction (Uni-directional).
• •Read Only Memory (ROM) is a type of storage medium that permanently stores data on personal computers (PCs) and other electronic devices. it is permanent and non-volatile, meaning it also holds its memory even when power is removed.
• RAM (Random Access Memory) is a temporary memory bank where your computer stores data it needs to retrieve quickly. RAM keeps data easily accessible so your processor can quickly find it without having to go into long-term storage to complete immediate processing tasks.
• Registers are a type of computer memory used to quickly accept, store, and transfer data and instructions that are being used immediately by the CPU. A register must be large enough to hold an instruction
• Flags are a modified kind of register that record the condition of a microprocessor's calculation. For instance, a "zero status" flag is activated only when the microprocessor's calculation concludes with a "zero" status.
• Flag Register contains a group of status bits called flags that indicate the status of the CPU or the result of arithmetic operations.
• There are two types of flags:

  
  

  The status flags which reflect the result of executing an instruction. The programmer cannot set/reset these flags directly.

  
  

  The control flags enable or disable certain CPU operations. The programmer can set/reset these bits control the   CPU's operation.
• Sequential logic circuits can be divided into the following three main categories:

  1. Event Driven – asynchronous circuits that change state immediately when enabled.
  2. Clock Driven – synchronous circuits that are synchronized to a specific clock signal.
  3. Pulse Driven – which is a combination of the two that responds to triggering pulses.
• The SR flip-flop, also known as a SR Latch, can be considered as one of the most basic sequential logic circuit possible.