Synchronous Sequential Logic Flashcards
What do Sequential Circuits consist of?
- Inputs
- A combinational circuit
- Memory elements
- A feedback path from memory elements to the combinational circuit
- Outputs
What are memory elements?
Memory elements are devices that store binary information. They define the current state of the circuit
What are Synchronous Sequential Circuits?
Are circuits where changes of state occur at discrete instants of time
True or False: Flip-flops are memory elements in a synchronous sequential circuit
True
True or False: Both Latches and Flip-flops are used as memory elements in clocked sequential circuits
True
What is the main difference between Latches and Flip-Flops?
Latches are controlled by signal levels.
Flip-flops are controlled by signal transitions (i.e. the rising or falling edge of a CP).
What are the problems level-triggered latches have?
- They may oscillate if the CP is too wide
- Outputs will be incorrect if the inputs change before the CP return to 0
What is the solution to level-triggered latches?
Solution: Trigger the device on the rising or falling edge of the CP
This is what master-slave and edge-triggered flip-flops do
What is the Master-Slave D Flip-Flop constructed with?
Is constructed with:
- A master D latch
- A slave D latch
- An inverter
What is the purpose of an inverter in the Master-Slave D Flip-Flop?
The inverter ensures only one latch is active at a time
What is the purpose of the J and K inputs in a JK Flip-Flop
J: acts as the set input
K: acts as the reset input
What is an advantage of the JK Flip-flop?
It avoids indeterminate states.
How is a T Flip-Flop created?
T flip-flop is created by connecting the J and K inputs of a JK flip-flop together.
This input is called T (Toggle)
What happens if T = 1 in a T flip-flop?
If T = 1 and a CP arrives, the outputs are complemented (toggled)
What are Direct Inputs?
- Allows one to set or clear a flip-flop asyncronously
for example, without a CP
