8085 Architecture

The 8085 microprocessor, introduced by Intel in 1977, is an 8-bit microprocessor that uses a single +5V DC power supply for its operations. It’s a successor to the 8080 microprocessor and is known for its simplicity, making it a popular choice for beginners learning about microprocessor architecture.

Key Features of the 8085 Microprocessor:

1. 8-bit Data Bus: It can process 8 bits of data simultaneously.
2. 16-bit Address Bus: It can address up to 2^16 = 65,536 different memory locations.
3. Clock Speed: Typically operates at 3 MHz.
4. On-chip Clock Generator.
5. 74 Instructions: The 8085 has a rich set of instructions, which can be categorized into five groups: data transfer, arithmetic, logical, branching, and machine control operations.
6. Five 8-bit Registers: B, C, D, E, H, and L which can also be paired as BC, DE, and HL.
7. On-chip Oscillator and System Controller.

Instruction Set Overview:

Here’s a brief overview of some of the 8085’s instruction set:

Instruction	Description (English)
NOP	No operation
MOV	Move data from source to destination
MVI	Move immediate data to a register
LXI	Load register pair with immediate data (e.g., LXI H,xxxx)
LDA	Load accumulator from memory
STA	Store accumulator to memory
LHLD	Load H and L registers from memory
SHLD	Store H and L registers to memory
ADD	Add register to accumulator
ADC	Add register and previous carry to accumulator
SUB	Subtract register from accumulator
SBB	Subtract register and previous carry from accumulator
INR	Increment register by 1
DCR	Decrement register by 1
INX	Increment register pair by 1
DCX	Decrement register pair by 1
CMA	Complement accumulator
CMP	Compare accumulator with register
JMP	Jump to specified address
JC	Jump if carry is set
JNC	Jump if carry is not set
JZ	Jump if zero flag is set
JNZ	Jump if zero flag is not set
CALL	Call subroutine
RET	Return from subroutine
PUSH	Push register pair onto stack
POP	Pop register pair from stack
RST	Jump to specific reset vector
DI	Disable interrupts
EI	Enable interrupts
HLT	Halt microprocessor

Applications of the 8085 Microprocessor:

The 8085 found its way into various applications due to its simplicity and ease of use. Some of its applications include:

• Traffic light control
• Temperature control systems
• Washing machines
• Calculators
• Basic computer systems

Conclusion:

The 8085 microprocessor, though considered primitive by today’s standards, played a pivotal role in the evolution of microprocessor design. Its simplicity and robust instruction set made it an ideal learning tool for students and hobbyists alike. Even today, it remains a fundamental part of many academic curriculums, offering a hands-on introduction to the world of microprocessors.