Timing Tutorial

TIMING TUTORIAL   [pic]prepared by Sridhar Ramachandran (GTA, CEG 360/560)

Timing, an important parameter associated with Sequential Circuit design will be discussed in this tutorial. We will begin with the general concepts associated with timing and then will proceed with examples to better understand their application to digital design. This tutorial consists of three sections.

PART 1 Introduction and terminology         

PART 2 Equations

PART 3 Example problems           

PART 1:  Introduction and terminology

========================================================================

A Digital System Design circuit can be characterized as a  'Combinational circuit' or a 'Sequential Circuit' and while calculating for Timing we will have to first identify what type of circuit is involved. 

---------------------------------------------------------------------------------------------------------------------------

Q1.How do we know, if given a circuit, whether it is a Combinational Circuit or a Sequential Circuit?

[Ans] If a circuit has only combinational devices (e.g.. gates like AND, OR etc and MUX(s))and no Memory elements then it is a Combinational circuit. If the circuit has memory elements such as Flip Flops, Registers, Counters, or other state devices then it is a Sequential Circuit.  Synchronous sequential circuits will also have a clearly labeled clock input.

---------------------------------------------------------------------------------------------------------------------------

Q2. Are the following circuits combinational or sequential?

[Ans][pic]

---------------------------------------------------------------------------------------------------------------------------

Q3. Why do we have to identify the type of circuit? Does it really matter?

[Ans]  It is important to identify the type of circuit because our timing calculation approach differs accordingly. Combinational circuits timing analysis deals primarily with propagation delay...