8085 Microprocessor Architecture & Operations
The 8085 is an 8-bit microprocessor that executes instructions by fetching, decoding, and executing them using its internal architecture, including registers, ALU, and control units. Understanding its components and addressing modes is crucial for programming and interfacing.
Core Principles
- The 8085 architecture consists of key functional blocks: Accumulator, ALU, Flag Register, General Purpose Registers, Program Counter, Stack Pointer, Instruction Register & Decoder, Timing & Control Unit, and Buffers.
- Registers serve specific purposes: Accumulator for data manipulation, General Purpose Registers for temporary storage, Program Counter for instruction sequencing, and Stack Pointer for subroutine/interrupt management.
- The Flag Register stores status bits (Sign, Zero, Auxiliary Carry, Parity, Carry) indicating the result of arithmetic and logical operations, crucial for conditional branching.
- Addressing modes define how operands are specified in instructions, including Immediate, Register, Direct, Register Indirect, and Implied, affecting instruction flexibility and size.
- Instructions are executed through machine cycles like Opcode Fetch and Memory Read/Write, involving specific signal timings and bus operations.
- Memory interfacing involves connecting ROM and RAM using address lines, control signals (RD, WR), and address decoding to ensure proper chip selection and data access.
Formulas
- 4KB = 4096 locations
- 4096 = 2^12
- 8KB = 8192 bytes
- 8192 = 2^13
Quiz
- Which register in the 8085 microprocessor stores the address of the next instruction to be executed?: Program Counter (PC)
- What is the primary function of the Flag Register in the 8085?: To indicate the status of the result after an operation
- Which addressing mode specifies the operand directly within the instruction itself?: Immediate Addressing Mode