8085 Microprocessor MOV Instruction Timing Diagram: A Detailed Analysis

Visualize the execution of the MOV instruction in an 8085 microprocessor with this detailed timing diagram. This guide breaks down the instruction fetch and execution phases, explaining the behavior of key control signals (ALE, RD, WR, I/O/M, S₀, S₁) at each T-state, providing a clear understanding of microprocessor timing.

Timing Diagram of the MOV Instruction in a Microprocessor

The MOV Instruction

The MOV instruction is used to copy data from one location to another in a microprocessor. The data can be moved from one register to another, from a register to memory, or from memory to a register. A single byte of memory is usually required to store this instruction. Direct memory-to-memory data transfer is typically not supported.

Example: MOV B, C Instruction

Let's analyze the timing diagram for the instruction MOV B, C. This instruction copies the contents of register C into register B. It requires only one memory access to fetch the instruction (opcode and operands).

Instruction Details

• Opcode: MOV
• Operands: Destination register B, Source register C

Timing Diagram

The timing diagram for the MOV B, C instruction is shown below. We will assume that the instruction is stored in memory location 2000h. It is represented by 4 T-states (clock cycles), where each T-state has a length of approximately 100 nanoseconds.

Opcode Fetch (T₁-T₄)

(The timing diagram for opcode fetching is provided in the original text. It should be included here. The diagram should show the signals ALE (Address Latch Enable), RD (Read), WR (Write), I/O/M (Input/Output/Memory), S₀, and S₁ over time (T₁-T₄). A description of each signal and its behavior during the opcode fetch should be included.)

Conclusion

Timing diagrams are valuable tools for understanding how instructions are executed at the microarchitectural level. They illustrate the sequence of signals involved in each operation, providing insights into a microprocessor's internal workings.