The document discusses the timing cycles of a microprocessor including T-states, machine cycles, and instruction cycles. A T-state is one clock period. A machine cycle is the time required to complete an operation like memory access and can comprise multiple T-states. There are five types of machine cycles including opcode fetch, memory read/write, and input/output read/write. An instruction cycle is the total time to fetch and execute a full instruction and can include one or more machine cycles. Examples are provided to illustrate how different instructions take different numbers of T-states and machine cycles to complete.

1. INSTRUCTION CYCLE,
MACHINE CYCLE & T-STATES
by
Manish Tadhiyal

2. Contents
• T-states
• Machine cycle
• Instruction cycles
• Examples
• Frequency

3. T-States
One clock period is called a T-state.
One T-state
Clock
signals
Time period of clock

4. Machine Cycle
Machine cycle can be define as time required
by the microprocessor to complete an
operation of accessing memory or input /
output devices.
A machine cycle is comprise of some member
of T-states.

5. There are following 5 types of machine cycle
which the microprocessor can undergo:
1. OP code fetch cycle (4T-states)
2. Memory read cycle (3T-states)
3. Memory write cycle (3T-states)
4. Input / Output read cycle (3T-states)
5. Input / Output write cycle (3T-states)

6. Instruction cycle
An instruction cycle can be define as total time
required by the microprocessor to completely
fetch and execute an instruction.
An instruction cycle is comprised of one or more
number of machine cycles.

7. Examples:-
Lets take two different examples:-
• MOV A,B
here the move (MOV) command take the
one machine cycle which fetch only the
Op-code with 4T-states.
• MVI A,35H
here the move (MVI) command take the
one machine cycle and initializing A with
35H takes which fetch one machine cycle i.e.
Op-code+ memory read= 4T + 3T = 7T-states.

8. Frequency
Here frequency(clock frequency) is help us
to determine the time taken by the
microprocessor.
Usually 8085having the maximum
frequency of 5MHz.
By the using of the frequency we can able
to find out the time period of instruction
cycle.

9. Example
Lets take the above example of MVI A,35H
T=1/f
=1/(5*10^6)
T=0.2µs
Therefore
I.C= 7*0.2
= 1.4µs