Timing diagram of 8085

Answer 1

Timing Diagram is a graphical representation. It represents the execution time taken by each instruction in a graphical format. The execution time is represented in T-states.

Instruction Cycle:

The time required to execute an instruction is called instruction cycle.

Machine Cycle:

The time required to access the memory or input/output devices is called machine cycle.

T-State:

• The machine cycle and instruction cycle takes multiple clock periods.
• A portion of an operation carried out in one system clock period is called as T-state.

MACHINE CYCLES OF 8085:

The 8085 microprocessor has 5 (seven) basic machine cycles. They are

1. Opcode fetch cycle (4T)

1. Memory read cycle (3 T)

1. Memory write cycle (3 T)

1. I/O read cycle (3 T)

1. I/O write cycle (3 T)

• Each instruction of the 8085 processor consists of one to five machine cycles, i.e., when the 8085 processor executes an instruction, it will execute some of the machine cycles in a specific order.

• The processor takes a definite time to execute the machine cycles. The time taken by the processor to execute a machine cycle is expressed in T-states.

• One T-state is equal to the time period of the internal clock signal of the processor.

• The T-state starts at the falling edge of a clock.