Analysis of Clocked Sequential Circuits. Example of a Sequential Circuit. D flip-flops. Example: Start with A=0, B=0, x=0. A(next)=0 B(next)=0 Y(next)=0. What are A(next), B(next) and y(next) given that A=1, B=1 and X=1?. D flip-flops. Alternate State Table. State Diagram. - PowerPoint PPT Presentation
Analysis of Clocked Sequential Circuits
Analysis of Clocked Sequential CircuitsExample of a Sequential CircuitD flip-flops
Example: Start with A=0, B=0, x=0.A(next)=0B(next)=0Y(next)=0What are A(next), B(next) and y(next) given that A=1, B=1 and X=1?
D flip-flopsAlternate State Table
Each circle is a state
When x=1, y=0.State Diagram
Each circle is a state
When x=0, y=1.Detects 0 in the bit stream of data
Output is a 0 as long as input is a 1. The first 0 after a string of 1 transfers the circuit back to 00.Summary
Model a Clocked Sequential Circuit with Verilog
Use parameter to define constantsForm the next state from x and the current stateForm the outputfork.....join construction
Define states with parameterUpdate States
If reset is 0, set state to S0.
If reset is 1, update state with next_state.Implement the States Using State Diagram
Right click to add state and next_state to the waveform shown rightValid Mealy Output
S0S1S2S3Glitiches occur because x changes before the next rising clock edgeGeneral Structure of a Mealy Machine
Output depends on input as well as the stateThe circuit is in. (variable: state)
Synchronize the input with clock when using Mealy machine.
Output depends on the state, but not the input.Synthesis of Sequential CircuitStart with a state diagramAssign Binary Values to the StatesState Diagram for Sequence DetectorProblem statement:Design a circuit that detects a sequence of three or more consecutive 1s in a string of bits coming through an input lineState Diagram of the Word Description
Start with S0.if input is 0, stay in S0.if input is 1, go to S1.Once in S1if input is 1, go to S2.if input is 0, go to S0.Once in S2if input is 0, go to S0.if input is 1, go to S3.Once in S3,if input is 0, go to S0.if input is 1, stay in S3, set output to 1.
Output is 1 when the circuit is in S3, 0 otherwise.Assign Binary Value to the States
Use two flip-flops to represent states.Let x be the inputAnd y be the output
01234567Assign Binary Value to the States
Sequence Detector Circuit
Random NumbergeneratorSequenceDetectorMeasurement Results