FSM - Moore and Mealy machine | An Lê Duy - practicax.net

# Moore and mealy fsm dating, re: fsm: moore or mealy?

The FSM is a Moore machine because the output is a combinational logic function in this case a trivial one of the state alone.

## Moore Machine to Mealy Machine

Example moore machine A moore machine with nine states for the above description is shown on the right. The initial state is state A, and the final state is state I.

The outputs are computed by a combinational logic block whose only inputs are the flip-flops' state outputs. A common simplification places the output on the transition or in the state only when it is asserted. A typical electronic Moore machine includes a combinational logic chain to decode the current state into the outputs lambda.

Facebook Twitter Sequential machines can be designed in two different ways: The equivalent ASM charts are in Figure 8. There are design techniques to ensure that no glitches occur on the outputs during moore and mealy fsm dating brief period while those changes are rippling through the chain, but most systems are designed so that glitches during that brief transition time are ignored or are irrelevant.

### FSM: Moore or Mealy?

Input X must be stable throughout the high time of the clock to guard against ones catching problems. For the first 1, the transition has output 0. At the next rising edge, the input is sampled and the next state is determined, but this is not presented to the outputs until the falling edge at time step For example, an input sequence from the reset state starting with a 0 would fill in the missing transition from state Despite the Mealy machine's timing complexities, designers like its moore and mealy fsm dating state count.

The finite state machines you have seen so far are all Moore machines. We also associate explicit output values with each transition in the Mealy state diagram and each state in the Moore state diagram.

## Mealy to Moore and Moore to Mealy Transformation

The outputs can change immediately after a change at the inputs, independent of the clock. The state diagrams in this figure are labeled more completely than our previous examples. A slash separates the inputs from the outputs.

Conditional output boxes in the ASM chart usually imply a Mealy implementation. The outputs depend only on the present state.

## Moore machine

Now you can match the color of the transition lines in both Moore and Mealy and realize why some of the lines are merged and some are not. The machine can be in any one of up to four valid states.

Example Following is an example of Moore machine. With a single input and 2 bits of state, the example FSM has eight different transitions, two from each of four states.

Worked Example[ edit ] A sequential network has one input and one output.

We simply substitute the logic functions at the inputs into the excitation equations: The state table for this example is as follows: For example, we make explicit the transitions that cause the machine to stay in the same state. The sequence 1 1 1 1, tracing from state 00 to 11 to 10 to 01, would catch the remaining transition.

X now changes to 1, and at the next falling edge the state changes to So, no splitting of state in Moore machine.

### 4 Moore and Mealy Machine Design Procedure

In the Mealy model the output will go to the edges rather than the states Here we have to notice the states which can merge actually. The necessary outputs are simply listed in the state box.

And the number of combinations doubles for each additional input bit and doubles again for each state bit. This gives Moore machines an advantage in terms of disciplined timing methodology. We express the transition as "a 1 input in state 00 leads to state We would learn how to convert this Moore to its equivalent Mealy machine.

## FSM: Moore or Mealy?

The outputs depend on the present state and the present value of the inputs. The output Z and the state bit B are the same.

For every state with distinct outputs on incident edges, split it into as many states as number of distinct outputs Associate the edge output with the state Redirect the edge appropriately Define the new edges from the split states as per the original Mealy machine Example Following is an example of Mealy machine.

After a short propagation delay, the state becomes Any doubt, please drop a comment below. A transition to 1 causes it to change to state 01 after time step Arcs are labeled with the input conditions that cause the transition from the state at the tail of the arc to the state at its head. The outputs then stay the same indefinitely LEDs stay bright, power stays connected to the motors, solenoids stay energized, etc.

The input next changes to 0, causing the state machine to remain in state 10 at time step The sequence of events in Figure 8. Moore outputs are synchronous with the clock, only changing with state transitions.

Clocked sequential systems are one way to solve metastability problems. However, there is a synchronous variation of the Mealy machine, which we describe later.

Consider a finite state machine that asserts its single output whenever its input string has at least two 1's in sequence.