MICROPROCESSOR DIGI NOTES by ELECTRICAL ZINDAGI ⚡
📖 Table of Contents (TOC)
Jump to the section you need:
💡 Your Ultimate Microprocessor Study Guide: Concept to Code
🚀 Core Fundamentals & Terminology Explained (The DNA of Computing)
- A **Microprocessor (MPU)** is the Central Processing Unit (CPU) fabricated on a single integrated circuit (IC) chip, acting as the 'brain' of any digital system.
- The **ALU (Arithmetic Logic Unit)** is the core execution unit, responsible for all mathematical (add, sub) and logical (AND, OR, XOR) operations.
- **Registers** are small, high-speed storage locations within the MPU that hold data, instructions, and addresses temporarily for quick access by the ALU. (Think of them as a fast scratchpad.)
- The **Control Unit (CU)** orchestrates all MPU operations by generating timing and control signals, ensuring synchronized data transfer and instruction execution.
- **Bus** is a collection of wires used to transfer information; the three main types are Address Bus (unidirectional), Data Bus (bidirectional), and Control Bus (mixed).
- **Word Length** defines the number of bits the MPU can process at once (e.g., 8-bit, 16-bit, 32-bit), directly impacting its performance and computational power.
- The **Instruction Cycle** is the time taken to fetch, decode, and execute a single instruction, which consists of multiple machine cycles and T-states. (Short trick: IC = Fetch + Execute).
🏗️ Key Architectures & Components (Building the Digital Engine)
- The **Von Neumann Architecture** uses a single address space and bus for both program memory and data memory, leading to the famous 'Von Neumann Bottleneck' due to sequential access.
- The **Harvard Architecture** uses separate address spaces and buses for instructions and data, allowing simultaneous access and faster overall processing speed. (Ideal for high-speed DSP applications).
- The **Program Counter (PC)** is a 16-bit register that always stores the memory address of the **next instruction** to be fetched, automatically incrementing after each fetch.
- The **Stack Pointer (SP)** is a 16-bit register that holds the address of the **top element** of the Stack, a temporary LIFO (Last-In, First-Out) memory area in RAM. (Essential for handling subroutines).
- **Pipelining** is an advanced technique where the CPU breaks down instruction execution into stages (Fetch, Decode, Execute) and overlaps them to increase throughput (Instructions per clock cycle).
- **Accumulator (A)** is the most crucial 8-bit register in many simple architectures (like 8085) where the result of most arithmetic and logic operations is stored.
💾 Memory & I/O Interfacing (Communicating with the World)
- **Memory Mapping** is the process of assigning a unique address to every memory location and I/O port so the MPU can distinguish between them.
- **I/O Mapped I/O** uses separate instructions (IN/OUT) and a smaller address space (typically 8-bit) for peripheral devices, isolating them from memory.
- **Memory-Mapped I/O** treats I/O devices as memory locations, using the same instructions (MOV, LOAD) and address space as the main memory, simplifying the instruction set. (Used in advanced systems).
- The **Address Decoding** circuit (usually a set of logic gates or a decoder IC) is essential for selecting the correct memory chip or I/O device based on the address generated by the MPU.
- **Interrupts** are hardware or software signals that momentarily stop the MPU's current task and force it to execute a specific routine (ISR), enabling efficient handling of external events. (Example: Pressing a keyboard key).
- **Vectored Interrupts** automatically direct the MPU to the correct service routine address, unlike non-vectored interrupts which require the external device to provide the address.
🌟 The Classic 8085 Microprocessor (The First Lesson for Engineers)
- The **8085** is an 8-bit MPU, requiring a single +5V power supply, famous for its simple architecture and being the foundation of early personal computers and embedded systems.
- It has a **16-bit Address Bus**, allowing it to access $2^{16} = 64$ KB (Kilobytes) of memory, a crucial limitation compared to modern CPUs.
- The 8085 uses **multiplexed Address/Data Bus (AD0-AD7)** to reduce pin count, requiring an external latch (like the 74LS373) and the **ALE (Address Latch Enable)** signal to demultiplex the buses. (The biggest trick question in exams).
- Its **Flag Register** (or Status Register) consists of 5 flags: Sign (S), Zero (Z), Auxiliary Carry (AC), Parity (P), and Carry (C), which reflect the status of the latest operation.
- **RST 7.5, 6.5, 5.5** are the three maskable, vectored interrupts, with **TRAP** being the highest priority, non-maskable, and vectored interrupt (used for critical events like power failure).
- The **SIM (Set Interrupt Mask)** and **RIM (Read Interrupt Mask)** instructions are used to selectively enable/disable (mask) the RST interrupts.
✍️ Programming and Instruction Set (Speaking the MPU's Language)
- **Instruction Set** is the complete collection of commands (opcodes) that a microprocessor is designed to execute, categorized by function (data transfer, arithmetic, logic, control).
- **Addressing Modes** define the different ways the operand (data or address) is specified in the instruction; common types include Immediate, Register, Direct, Indirect, and Implied. (Short trick: **M**y **R**adio **I**s **I**n **D**anger).
- **Immediate Addressing** (e.g., `MVI A, 35H`) specifies the data directly within the instruction itself.
- **Direct Addressing** (e.g., `LDA 2050H`) specifies the exact 16-bit memory address of the data.
- **Register Addressing** (e.g., `MOV A, B`) uses a register name as the operand, leading to the fastest execution time.
- **Assembly Language** is a low-level programming language that uses mnemonics (like `ADD`, `MOV`) that are directly translated into machine code by an Assembler. (One mnemonic = one machine instruction).
- **Subroutine** (or procedure) is a block of code written separately to perform a specific task, called using the **CALL** instruction and terminated by the **RET** instruction.
**These notes are a must-have for your Electrical and Electronics competitive exam preparation!**
***Advertisement Break - Stay Tuned for More!***
We rely on these advertisements to keep delivering high-quality, free educational content like these Digital Notes. Thank you for your support!
🔗 May You Also Like These Electrical Zindagi Posts
| 🔥 Related Posts to Boost Your Knowledge (Backlinks) | |
|---|---|
| Detailed Notes on Digital Electronics Logic Gates | Top 50 Interview Questions for Power Electronics |
| Transmission and Distribution Concepts Simplified | Basics of Electrical Machines: DC Motor Explained |
🔔 Join Our Community for Regular Updates
| Stay Connected with Electrical Zindagi! | ||
|---|---|---|
| YouTube (Video Lessons) | Telegram (Quick Notes/Discussions) | WhatsApp Channel (Latest Updates) |
| Click to Subscribe | Click to Join | Click to Follow |
| LinkedIn (Professional Networking) | Email (Direct Communication) | |
| Connect on LinkedIn | electricalzindagi@gmail.com | |
🧡 Support the Electrical Zindagi Community 🧡
If these notes helped you master Microprocessors, consider a small donation. Your support helps us cover server costs, create more high-quality content, and keep this educational resource **free for all**!
🌟 Donate & Support Our Mission 🌟Click the button above to contribute securely.
🔍 SEO Keywords for Post Indexing:
microprocessor digi notes, 8085 microprocessor notes, 8086 microprocessor architecture, microprocessor instruction set, electrical zindagi microprocessor, microprocessor pdf, microprocessor fundamentals, ALU and control unit, addressing modes in 8085, non-maskable interrupts, difference between Von Neumann and Harvard architecture, MPU interview questions, how a microprocessor works.