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Design and Implementation of VLSI Systems_Lecture 07: Sequential Circuit Sign potx
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Design and Implementation
of VLSI Systems
Lecture 07
Thuan Nguyen
Faculty of Electronics and Telecommunications,
University of Science, VNU HCMUS
Spring 2011
1
LECTURE 07: SEQUENTIAL CIRCUIT
DESIGN
1 Introduction
2 Circuit Design of Latches and Flip-flops
3 Sequencing Static Circuits
2
4 Static Sequencing Element Methodology
5 Synchronizer
LECTURE 07: SEQUENTIAL CIRCUIT
DESIGN
1 Sequencing
2 Sequencing Element Design
3 Sequencing Methods
3
1 Introduction
2 Circuit Design of Latches and Flip-flops
3 Sequencing Static Circuits
4 Static Sequencing Element Methodology
5 Synchronizer
SEQUENCING
Combinational logic
Output depends on current inputs
Sequential logic
Output depends on current and previous inputs
Requires separating previous, current, future
Called state or tokens
Ex: FSM, pipeline
CL
clk
in out
clk clk clk
CL CL
Finite State Machine Pipeline
4
SEQUENCING (CONT.)
If tokens moved through pipeline at constant
speed, no sequencing elements would be
necessary
Ex: fiber-optic cable
Light pulses (tokens) are sent down cable
Next pulse sent before first reaches end of cable
No need for hardware to separate pulses
But dispersion sets min time between pulses
This is called wave pipelining in circuits
In most circuits, dispersion is high
Delay fast tokens so they don’t catch slow ones.
5