Machines that can remember Actions, & Patterns of Actions

What are the two things machines remember?
The two things machines remember are:

  1. Actions.
  2. Patterns of actions.

What are the three characteristics of automatons?*
The three characteristics of automatons are that they:

  1. Operate on a single command.
  2. Memorize a sequence of mechanical actions.
  3. Don't take user input.

Memory and State

...

What does it mean when the state of an automaton is stable?
When the state of an automaton is stable, it means that it will not change unless done by some external force.

What does it mean when the state of an automaton is well-defined?
When the state of an automaton is well-defined, it means that only a specific set of actions will be performed during the state.

What causes an automaton to switch from state to state?
An automaton switches from state to state because of an external force.

Summary

The states of an automaton are stable and well-defined.

A state is stable when it doesn't change unless by some external force. A state is well-defined when only a specific set of actions are performed during that state.

An automaton changes state by some external force.

Multi-State Machine

What does the state of a multi-state machine affect?
The state of a multi-state machine affects the behavior.

What does the circuit of a multi-state machine already have inside?
The circuit of a multi-state machine already has the circuit blocks for executing ADD, SUB, MUL, MOD, etc.

What does the multi-state machine do with the circuit blocks?
The multi-state machine chooses which circuit blocks to activate depending on its state.

Todo

The slide mentions that a multi-state machine could potentially use a multiplexer to determine which circuit block is activated. That multiplexer's control signal is determined by the state number.

Latches

What does a latch do?
A latch remembers something for as long as it is asked to.

How does a latch operate?
A latch operates by looping mutual or complementary conditioning infinitely.

What is a latch?
A latch is a state holder, preserver, and sustainer.

What is the circuit diagram for a latch using two inverters?
The circuit diagram for a latch using using two inverters is:
2 Inverter Latch.png

Latch with Set / Reset (SR-Latch)

What is the circuit diagram for a latch with a set and reset signal?
The circuit diagram for a latch with a set and reset signal is:
Latch With A Set And Reset Signal.png

What is the truth table for the SR-Latch?
The truth table for the SR-Latch is:

Action
Hold 0 0 0 or 1
Toggle 1 1 0 1
Toggle 2 0 1 0
DNC 1 1 0

Do we care if and are both set to 1?
No, we don't care if and are both set to 1.

SR-Latch Mechanism

What is the hold state of an SR-Latch?
The hold state of an SR-Latch is when and are set to 0 and the value of remains the same.

What happens when is set to 1 during the hold state?
When is set to 1 during the hold state, is set 1 and enters the hold state again.

What happens when is set to 1 during the hold state?
When is set to 1 during the hold state, is set to 0 and enters the hold state again.

Complementary SR-Latch

What is the circuit diagram of a complementary SR-Latch?
The circuit diagram of a complementary SR-Latch is:
Complementary SR-Latch.png

Locking or Unlocking an SR-Latch

What signal enables the set and reset signals?
The signal that enables the set and reset signals is the clock signal.

How does a clock signal lock an SR-Latch?
A clock signal locks an SR-Latch by preventing the and inputs from passing through.

What is the circuit diagram for an SR-Latch with a clock signal?
The circuit diagram for an SR-Latch with a clock signal is:
SR-Latch With A Clock Signal.png

...

Clocking creates Memory

What happens when the clock signal is 0?
When the clock signal is 0, and can't affect .

What happens when the clock signal is 1?
When the clock signal is 1, and can affect .

What is the truth table for a complementary SR-Latch?
The truth table for a complementary SR-Latch is:

Clock
0 0 0 Hold (Locked)
0 0 1 Hold (Locked)
0 1 0 Hold (Locked)
0 1 1 Hold (Locked)
DNC
1 0 0 Hold
1 0 1
1 1 0
1 1 1 DNC

...

Using Clocking as a Timer for Toggling

What is it called when changes to a component's state are controlled by a clock signal?
When changes to a component's state are controlled by a clock signal, it is called being synchronized with the clock signal.

Synchronous Circuit

What are the characteristics of a synchronous circuit?
The characteristics of a synchronous circuit are:

  • It can only toggle when there is an active clock signal.
  • It holds its state or value when the clock is inactive.
  • The last toggle by the end of the active clock signal is held and remains until the next active clock signal.
  • The duration of how long it holds its state or value is equal to at least the clock signal period.

D-Latch

What is a D-Latch?
A D-Latch is a latch with a single input that controls the set signal and the reset signal .

What is D-Latch short for?
D-Latch is short for Data Latch.

What is the circuit diagram for a D-Latch?
The circuit diagram for a D-Latch is:
D-Latch.png

What is the truth table for a D-Latch?
The truth table for a D-Latch is:

Clock
0
1 0 0
1 1 1
Summary

A D-Latch is an SR-Latch that requires less effort to use.

Understanding D-Latch

Is a D-Latch level-triggered or edge-triggered?
A D-Latch is level-triggered.

What does a D-Latch act like when there's an active clock signal?
When there's an active clock signal, a D-Latch acts like a buffer.

What does a D-Latch act like when there's an inactive clock signal?
When there's an inactive clock signal, a D-Latch acts like a memory cell.

What does a D-Latch hold and until when?
A D-Latch holds the state of the machine until the next active clock signal.

What do you need to do if you want the D-Latch to retain the state during the next active clock signal?
To retain the state during the next active clock signal, don't change the value of .