The 8085 Microprocessor comprises various functional blocks, each with a specific purpose. The functional blocks include Accumulator, Temporary Register, Arithmetic and Logic Unit (ALU), Flag Register, Instruction Register, Instruction Decoder and Machine Cycle Encoder, General Purpose Registers, Stack Pointer, Program Counter, Incrementer/Decrementer, Timing and Control Unit, Interrupt Control, Serial I/O Control, and Address Buffer and Address/Data Buffer.
The following are the functional blocks in the 8085 Microprocessor.
- Accumulator
- Temporary register
- Arithmetic and Logic Unit (ALU)
- Flag register
- Instruction Register
- Instruction Decoder and Machine cycle encoder
- General purpose registers
- Stack Pointer
- Program Counter
- Incrementer / Decrementer
- Timing and Control unit
- Interrupt control
- Serial I/O control
- Address buffer and Address / Data buffer
The Accumulator, also referred to as the A-register, is an 8-bit register that is associated with the ALU. It holds one of the operands during arithmetic or logic operations and the result of these operations is stored in the Accumulator.
The Temporary Register, TEMP, is another 8-bit register associated with the ALU. It is used to temporarily store data during arithmetic or logic operations.
The ALU performs arithmetic and logic operations on 8-bit data and includes the Accumulator, Temporary Register, arithmetic and logic circuits, and Flag Register. The results of these operations are stored in the Accumulator and indicated in the Flags.
The Flag Register, also referred to as the Status Register or Condition Code Register, is an 8-bit register with five flags: Sign (S) Flag, Zero (Z) Flag, Auxiliary Carry (AC) Flag, Parity (P) Flag, and Carry (CY) Flag.
The Instruction Register is an 8-bit register that stores the instruction fetched from memory. The Instruction Decoder and Machine Cycle Encoder unit decodes the instruction stored in the Instruction Register.
The General Purpose Registers are six 8-bit registers named B, C, D, E, H, and L, with two additional 8-bit temporary registers, W and Z. The B and C registers can be combined as the BC register pair, and similarly, the D and E registers can be combined as the DE register pair, and the H and L as the HL register pair.
The Stack Pointer is a 16-bit register used as a memory pointer for the stack in memory. It is used to store data in a FILO (First In Last Out) buffer during subroutine operations.
The Program Counter is a 16-bit register that points to the next instruction to be fetched from memory. The Incrementer/Decrementer unit increments or decrements the contents of 16-bit registers.
The Timing and Control Unit contains the internal clock generator and micro programs for all instructions to carry out microsteps. The Interrupt Control and Serial I/O Control manage interrupt requests and serial input/output, respectively. The Address Buffer and Address/Data Buffer are used to temporarily store addresses and data during operations.