107 Flashcards
What is sequential logic?
This is a logic circuit which depends on both the current input and previous values of input
What is combinational logic?
This is a logic circuit which depends on only the current inputs
What is a clock siganl
It is a square wave electrical signal with a frequency called the clock frequency
When does a circuit with a clock cycle update?
On a clock edge
What are the two clock edges?
> Rising edge / Positive edge
> Falling edge / Negative edge
What type of circuit does not use a clock signal?
This is an asynchronous circuit
How is a positive clock represented on a logic element?
A triangle into the circuit element.
Looks like: =>
How is a negative clock represented on a logic element?
A triangle with a dot into the circuit element.
Looks like: =°>
What is a d-latch? (4)
> This is a fundamental sequential logic circuit component
It is bistable
When the enable gate is powered the output will take the value of the input
When the enable gate is not powered the output will hold its value
What is an Astable Multivibrator?
A component that oscillates between two values
What is a monostable multivibrator?
> A component that can be put into a state but has a single stable state and will return to that stable state after a while of being in a different state
Also called a one-shot
What is a D-Flip-Flop? (3)
> A data/delay flip flop
The output is delayed by a lock cycle compared to the change of input
Constructed from D-Latches
What are the inputs and outputs?
Inputs > D - Data > E - Enable Outputs > Q - Stored Value > NotQ - Inverted stored value
What is the truth table for a D-latch?
E D Q Qnot 0 0 NC NC 0 1 NC NC 1 0 0 1 1 1 1 0
NC - No change
What is the circuit for a dlatch?
> 4 NAND logic gates (A topleft, B topright ,C bottomleft, D bottomright) > Data goes into A > Enable goes into C and A > Output of A goes into C > Output of A goes into B > Output of C goes into D > Output of B goes into D > Output of D goes into B > Output of B is Q